Like what 3rd party sites
i cannot say here if not its like openly promoting the sites, u just search for buy/sell skin for cs or dota, u will see many different sites offering different method for payout and the diff % transaction. so if u buy a skin from the community market for 100, u can resell it lower at these sites for 80, after tax u get like 70, directly in ur physical wallet rather than the 100 stuck in the steam wallet where u can only buy games or items from steam directly.
some ppl also buy games and sell it cheaper than steam to other users to get the money, but its harder this way as ppl will think that u might be scamming or what.
anyway u get the idea la.