Well, since you asked:
Episode 1: “The Old Republic”: Nearly a thousand years before the Battle of Yavin, a young Yoda is discovered on his home planet by his master-to-be, brought to the Jedi Temple, and trained as a Jedi. Some sort of conflict occurs and several dozen Jedi leave the order, forming a rival order known as the Sith. War ensues.
Episode 2: “Rule of Two”: Jumping through hundreds of years of the conflict between the Jedi and the Sith, we see the Sith whittled down to two; eventually the Sith are believed to be destroyed entirely, but have really been driven underground. We learn why the Sith henceforth don’t expand beyond their one master and one apprentice structure, and we watch as successive Sith pairs conduct a clandestine terrorist campaign against the Jedi and the Republic.
Episode 3: “Revenge of the Sith”: Darth Plagueis and his apprentice Darth Sidious plan and begin to execute the elaborate revenge of the Sith, all the while hidden in plain sight from the weakened Jedi order. Sidious secretly takes his own apprentice, Darth Maul, launches his political career using his Palpatine alter ego, and destroys his master. The story of the Clone Wars and collapse of the Republic, with Anakin, Obi-Wan and Padme as the prominent players we all know, unfolds.