What is the difference between scull and sweep oars?

Sculling = One oar in each hand and a sliding seat. Usually 1,2, or 4 rowers written as 1x,2x,4x. Steering can be done by varying the amount of pull on each side. Sweep rowing = Two hands on one oar. Each rower takes one side (port/starboard) so there needs to be an even number of rowers. Sliding seat. 2,4, or 8 rowers. Often (and always with 8 rowers) has a coxswain to steer and coordinate. Rudders is used. Usually written as 2+,4+, 8+ (rowers w/coxswain) or 2-,4- (w/o coxswain)