#2 - March 18, 2014, 11:03 p.m.
The Horadric Cache is a reward given to players for completing Adventure Mode Bounties in Reaper of Souls. They'll always contain items based on the level it was awarded from, so waiting to open one until you're higher level will not increase the level of rewards. Feel free to open up those Horadric Caches right away, since they might have gear or crafting materials that will immediately help you in your journey.