The tub carries clothes to the top, then drops them in the water. Because tumblers need a large tub, it is difficult to enlarge overall washer size. Because of this, capacity is only about ten pounds, but a correspondingly moderate amount of water is required. Agitation washers load from the top. They wash with an agitator that moves back and forth, up and down in combination with a movable wash basket.
Capacity is one of the most important features of agitators.
A full load for most is 18 pounds. This allows you to wash in one load what used to require two. It also means you can wash as many as four large items like sheets at one time. Because you won't always have full loads, agitators have water level settings ranging from a few items to not quite a full load. If you live in an apartment or don't want a large capacity washer, there are compact models that wash smaller loads and fit into limited space.