There's three ways a ship (air or water) can move. If you imagine axes, two horizontal, one running the length of the ship (x), one running across the ship (y) and one vertical, running up and down through the middle (z). Rotation about the x-axis is called roll, rotation about the y-axis is called pitch, z-axis rotation is called yaw. In an airplane roll is when the wings go up and down alternately, pitch is when the nose goes up or down and yaw the nose waggles back and forth relative to the direction of travel.

So, basically what jheem said only more specific and less understandable.