If the torso rotates, then the ''body'' is performing angular motion.
Most human angular motion movements rotate around an axis that is parallel to the spine (i.e., a longitudinal axis). When the body is not in contact with the ground, the longitudinal axis is the spine. When the body is in contact with the ground, the longitudinal axis is most often the long axis of the supporting leg. However, the axis of rotation can also be the spine. Examples are throwing a baseball, hitting a golf ball, kicking a soccer ball, and hitting a tennis forehand.
Movements like a somersault, a cartwheel or spiking a volleyball are examples of movements that cause the torso to rotate around different axes. A somersault is a torso rotation around a medial-lateral axis. A cartwheel is a torso rotation around an anterior-posterior axis. Spiking a volleyball is torso rotation around a medial-lateral axis.
This makes explaining linear motion movements pretty easy. They are movements that do not cause the torso to rotate. Examples are jumping, running, walking, and riding a bicycle.