Requests are the flyers found on the board under Mirajane's attention. This is your main source of Guild Points, Jewels, and Bond points. This will be a casual unlock as you need to run requests for pretty much everything. Simple story requests as well as the rank-# missions can be done at least once, while Regular requests will show back up once you've completed all ten of that rank.
You should get this as part of the Guild Rank C goals anyway.