It's like team work. This principle is described in more detail in Truss Fun. Loads on Structures Loads are classified as different types. The load type is also the type of stress caused in a structure. Loads are caused by lots of different conditions as described later.
Tension is a load which stretches or lengthens a structure.
Easily demonstrated by pulling a piece of clay. Compression is a load which shortens or compresses a structure. Shear makes the structure slide one piece over another. Torsion twists a structures. Loads come from the forces which are placed on a structure.