I'm playing Rock Band 3 and completed a Goal. What do I do with these coins?

You can complete Rock Band World Goals while playing Rock Band 3 -- some Goals may even be specifically created for Rock Band 3 -- and you'll earn badges and coins on your Rock Band World profile. The coins you earn for completing Goals are used to purchase Power-Ups in Rock Band Blitz; if you don't own Rock Band Blitz, the coins will just accumulate on your Rock Band World profile until you buy and link Rock Band Blitz.