Short answers, pulled from the story.
Epicureanism was founded in 307 BCE by Epicurus, an ancient Greek philosopher born in 342 or 341 BCE on the island of Samos. Epicurus established his school at a property in Athens known as the Garden.
Epicurus held that pleasure was the chief good and pain the chief evil, but he defined the greatest pleasure as the complete removal of all pain, both physical and mental. He called these states aponia (absence of bodily pain) and ataraxia (freedom from mental disturbance), and he advocated modest, sustainable pleasure over sensual excess.
Epicureanism teaches that death is nothing to fear because the soul is mortal and material, dissolving with the body at death. Since there is no sensation after death, the person who has died cannot be harmed. This view gave rise to the Epicurean Epitaph: "Non fui, fui, non sum, non curo" (I was not; I was; I am not; I do not care), found on many gravestones of the Roman Empire.
Epicureanism does not deny that gods exist but insists they have no involvement in human life or the universe. Whether the gods exist as actual material beings in the space between worlds (the realist view) or as idealized images of the best human life (the idealist view) remains a scholarly dispute, with the realist interpretation currently more widely held.
Epicureanism had largely disappeared by the late 3rd century CE, displaced by the growing dominance of Neoplatonism, Peripateticism, and eventually Christianity. The school had flourished through the Late Hellenistic period and the Roman Empire before this decline.
The Epicurea is a collection of texts, fragments, and testimonies by Epicurus assembled by Hermann Usener in 1887. It gathers Epicurus' surviving writings explaining the values and beliefs of ancient Epicurean philosophy, and it remains a key resource for reading the philosopher's actual words alongside the three letters preserved by Diogenes Laertius.