The Mishnah establishes that all of Israel has a portion in the World to Come (Mishnah Sanhedrin 10:1), and the Gemara in Berakhot 17a describes its character directly: there is no eating, drinking, procreation, business, jealousy, hatred or competition there, but rather the righteous sit with crowns on their heads, basking in the splendor of the Divine Presence, likened to the eating and drinking of 'they beheld God and they ate and drank.'
The Rambam codifies this teaching, ruling in Mishneh Torah, Repentance 8:2 that the World to Come has no body or physicality at all, only the souls of the righteous existing without bodies like ministering angels, and therefore none of the bodily needs of this world apply there; he further teaches in Mishneh Torah, Repentance 8:1 that this is the good without death and without evil, identified with the phrase 'that it may be well with you... and that you may prolong your days' understood as referring to an entirely good, entirely long world. Yet in Mishneh Torah, Repentance 8:7-8 he cautions that no human being has the capacity to grasp the true greatness, beauty and power of that good, which is known to God alone, distinguishing it from the physical blessings promised for the messianic age.
Pirkei Avot frames this world as a corridor before the World to Come, a banquet hall, urging preparation in the corridor so as to enter the hall properly (Pirkei Avot 4:16), while Daniel speaks of an awakening of those who sleep in the dust, some to eternal life and some to reproach, with the wise shining like the brightness of the sky (Daniel 12:2-3), and Yeshayahu foretells that death will be swallowed up forever and tears wiped from every face (Yeshayahu 25:8).
The Gemara in Sanhedrin 90b-91a derives resurrection itself from the pasuk 'you who cleave to the Lord your God are all alive today,' reading it to mean that even on the day when all others die, those who cleave to God will live, and records Rabbi Meir's exchange with Cleopatra about how the resurrected will be clothed. Taanit 31a adds a vivid scene of the future: the Holy One will make a dance for the righteous in Gan Eden, with each pointing and declaring 'this is our God for whom we waited.'
Several sources describe intimations of the World to Come already present in this world. Berakhot 57b teaches that Shabbat, sunlight, and the relief of bodily function are each 'a sixtieth' or a semblance of the World to Come, and Chiddushei Aggadot, Shabbat 23 similarly holds that mitzvot performed with wine and other acts give a person a taste of the World to Come even now, this world containing in literal form what a person prepares for. Notes by Rabbi Yehoshua Hartman on Derekh Chayim 6:7:91 records the teaching that the generation of the flood was given a taste of the World to Come in this world precisely so they would know what good they had forfeited.
The philosophical and kabbalistic tradition emphasizes that the World to Come consists of intellectual or spiritual attachment to God rather than sensory pleasure. The Kuzari describes it as the soul separating from the senses to behold the supernal world and hear the Divine word (Kuzari 1:109), the Rambam's commentary on the Mishnah calls its pleasure one that cannot be divided into parts or compared to anything in this world (Rambam on Mishnah Sanhedrin 10:1), and the Guide for the Perplexed describes the increase of intellectual apprehension and joy as the body's forces weaken with age, culminating in the death by a kiss experienced by Moshe, Aharon, and Miriam (Guide for the Perplexed, Part 3 51:21-22). Mesillat Yesharim similarly describes complete detachment from the physical and constant clinging to God as the mark of one who already lives this reality (Mesillat Yesharim 26:2-4), and Nefesh HaChayim speaks of the soul rising and attaching, little by little, to the 'bundle of life' with God according to one's Torah, service, and purity of heart (Nefesh HaChayim, Gate I 18:1).
Chassidic and kabbalistic sources stress a future revelation that transforms this world itself. The Tanya teaches that the culmination of the Messianic era and resurrection is the revelation of the light of the Ein Sof within this material world itself, so that this world's vitality ascends to become a vehicle for God (Tanya, Part I; Likkutei Amarim 37:1), and separately that the righteous will receive strength to endure the revealed Divine light without being nullified, seeing their Teacher without any concealment (Tanya, Part I; Likkutei Amarim 36:6-7). Likutei Moharan describes the World to Come as a day that is entirely long, beyond time altogether, so that all the time of this entire world is as nothing compared to a single moment there (Likutei Moharan, Part II 7:6).
Several works distinguish stages or senses of 'Olam HaBa.' The Ramban's Shaar HaGemul distinguishes Gan Eden, the reward of the soul immediately after death, from the World to Come proper (Sha'ar HaGemul of the Ramban 49), and the Recanati elaborates that souls first enter a lower Gan Eden to become accustomed to the supernal light before ascending further, citing the Ramban's view that the body's power persists for twelve months after death (Recanati on the Torah, Bereshit:194). The Shelah likewise lists three distinct phases — life of the World to Come, the messianic era, and resurrection of the dead, each with its own character (Shenei Luchot HaBerit, Torah Shebikhtav, Shoftim, Derekh Chayim:10), and Torat HaAdam insists that the Olam HaBa referred to throughout is not the world of souls received immediately after death but a world God will renew after the messianic era and resurrection (Torat HaAdam, The Gate of Recompense). The Radbaz similarly discusses two distinct resurrections, one particular to the righteous who died in exile and one general, tied respectively to the coming of the messiah and to the ultimate world of resurrection (Teshuvot HaRadbaz Volume 3 1069:2-3), and Sefer HaIkkarim treats the scope of resurrection — whether limited to the completely righteous or extending to the broader nation — as a point on which the sages themselves differed (Sefer HaIkkarim, Maamar 1 23:6).
Modern expositions bring these strands together. Peninei Halakhah explains that the World to Come unfolds in two stages — first the soul's ascent at death to the world of souls containing Gan Eden and Gehinom, and then, after the resurrection, the reunification of soul and body in unending elevation (Peninei Halakhah, Days of Awe 1:5), and Hegyonei Uziel similarly speaks of two senses of Olam HaBa, the world of souls (reward) and the world of resurrection, both flowing from the promise that all of Israel has a portion in the World to Come (Hegyonei Uziel, Gate III 43:2). The notes on Netivot Olam likewise clarify that the Gemara's statement that there is no eating or drinking in the World to Come refers specifically to the reward-world, where the righteous no longer need sustenance because their continued existence was already granted before entering it (Notes by Rabbi Yehoshua Hartman on Netivot Olam, Netiv Hatorah 10:164).
Other sources add further color: Maamar HaGeulah, Chapter 4 4:3 describes an unceasing joy and perpetual flow of delight for souls beyond even the sustenance they receive; Beit Yaakov, Vaera 3 holds that each person's chief pleasure will be closeness to God calibrated to the closeness earned in this life; Ner Mitzvah V'Torah Or Shaar HaEmunah דף סא, ב distinguishes a hidden supernal delight reserved for Olam HaBa from a lesser revealed delight experienced in Gan Eden; Chiddushei Aggadot, Sanhedrin 91 describes a future unification of perception in contrast to this world's division; Sulam on Zohar, Miketz 99:1 associates the World to Come with a pleasantness from which all the lights of the world shine and divide; Shiurei Daas 1 p. 18 depicts it as resembling Eden where the soul rises and unites with lofty, pure worlds in sacred pleasure unlike anything in this world; and Shiurei Daas 1 p. 105 emphasizes simply that the World to Come is itself a world, and the primary one.
On the question of whether the dead retain any awareness, Berakhot 18a:13-14 records a dispute in which Rabbi Chiyya insists the dead do know what transpires among the living, countering the verse 'the dead know nothing' by distinguishing those who die unaware from the righteous who remain spiritually alive even in death. Separately, Kiddushin 82a:9-10 teaches that Torah study yields reward both in this world and a principal reward preserved for the World to Come, unlike other pursuits whose reward is confined to this world, and Maamarim Melukatim ש"פ אחרי, מבה"ח אייר ה'תשמ"ו distinguishes Gan Eden, accessible even now, from the future resurrection of the dead, whose greater revelation is the primary sense of Olam HaBa promised to all Israel.