The document discusses using vectors to determine relative motion and velocities between objects. It contains examples of calculating the relative velocity between two trains moving in opposite directions, an airplane's velocity relative to the ground when factoring in wind speed and direction, and determining the angle an airplane needs to fly to compensate for wind and travel due east relative to the ground. The document outlines two main types of relative motion problems - finding an object's velocity relative to the ground given its motion and a medium's motion, and calculating the angle an object needs to travel to compensate for a medium's velocity.