From Diablo Wiki
Patch 2.1 is the first content patch for Reaper of Souls. New features wil include Seasons; ladders for brand new characters to work their way up. There will be seasonal Legendaries and Leaderboards to track achievements and conquests allowing players to compare progress against friends and clan members. A new type of Rift the Greater Rift will see players race against the clock to kill monsters and progress to higher difficulty Greater Rifts. Rift Guardian's will drop much better loot. Greater Rift progress will be recorded on a special leaderboard. There are changes to skills, class resources and health provisions. Patch 2.1 will appear on the PTR first and once ironed out rolled out onto the live server.