Daedra are on the loose on the continent of Tamriel as Oblivion Gates open across Cyrodiil! And it's up to you to save it (or ignore it if you'd rather).
The Elder Scrolls IV: Oblivion is the sequel to Morrowind and as was also true with the former, Oblivion allows you to do whatever you want, travel wherever you want, and play however you like. Play as an assassin, thief, wizard, alchemist, warrior, archer, or as any combination you desire! With ten races to choose from: four human, four elven, and two beast; the sheer number of different ways to play Oblivion are staggering.
As an RPG you create your character from scratch, picking their race, basic attributes, skills, and specializations, along with even more options. The main quest revolves around saving the land from daedra (demon-like beings) who keep appearing through Oblivion Gates (rift portals) and closing their access to the world of Nirn, which will be easier said than done. How you do it or if you do it, is up to you.