What is GTA Online?
GTA Online is an instanced online world with a free roam hub that connects players to PvE missions, PvP races, PvP death match modes, PvP versus missions and a number of other miscellaneous activities (including golf, tennis and darts).
Some simple content is played inside the instanced free roam world such as car exports, target kills, impromptu races and one on one death matches but most is played from smaller job lobbies from which you can invite members of your session, crew or friends list.
Aim types are separated into different free roam instances.
Your character progression is indicated by level and the collection of money and assets (vehicles, apartments, weapons). Access to weapons and jobs are governed by this level. You start with nothing but a pistol and your wits but hopefully will soon become a fully fledged criminal machine with access to an array of supercars, helcopters, planes and weapons.