It is part of a compensation plan first used as 2-up by an australian marketer, mainly consist in pass x amount of direct referrals to qualify (And start earning money), the same will happen with your next referrals, they will pass x of their direct referrals to you. This plugin is available for unilevel, board plan and forced matrix systems.
Some prosperity systems use after the x-up qualification a variant, for example to keep 4 and give 2 after the 2 required referrals to qualify, and can happen unlimited times. For a better explanation lets take this example, if a member refer 12 people into the system, the first 2 go to his sponsor and qualify to enter the system (unilevel, board, forced matrix), the next 4 referrals goes under him, the next 2 goes to his sponsor again (coded to the sponsor) and the last 4 on the explanation goes under him again.
The X-up plugin cost $50.00 and the X-up with the keep X and give Y variant cost: $100.00