Trade Paperback.
With comics they usualy just collect a single story arc, ie all the issues of a story arc back to back, and a cover gallery is pretty standard, but sometimes some TPBs have extra things aside from a cover gallery, like sketches, concepts, exclusives, etc, etc.
So in short the first SF TPB will probaly collect everything published between Issue #0 and Issue #? (whatever number the end of the first story arc is)