When Patch 1.2 went live in Star Wars: The Old Republic, it introduced players to the Legacy system. In a nutshell, what the Legacy system boiled down to was giving players an assortment of upgrades they could earn by playing more - level a character to 50 and you unlock that character's race for all subsequent alts; finish the class stories and you earn cool abilities; plus a handful of other unlocks. These unlocks were legacy-wide - they affected all characters on that account on that server.
Patch 1.3: Allies builds upon the legacy of the Legacy patch, but the upgrades are per-character instead of global. These new upgrades allow players to follow a narrower, more specialized leveling path for their new alts. While the initial offerings of the Legacy system were intended to add flavor and style, the Perks system gives players the tools they need to make leveling new Legacy alts quicker and more efficiently.
Read more about how to give your character a razor-sharp focus with our Legacy Perks Guide.