its the samething they do for csgo. They give you mission to do on certain maps or use certain weapons and gather kills/points the main difference is that in csgo you have to wait for the match to completely end to get your item, in tf2 you get your item as soon as you finish the mission and turn it in. Finally like csgo their are two sets of weapons the first are ones that can only get through mission and odds are there will be some nice rare ones you might want to get. The other set is from crates only which has a chance to be strange/unusual/unsual-strange/normal