Visual Tension
A sense of unresolved energy created by elements that pull against each other or against the frame.
In depth
Tension comes from near-misses and imbalance: two figures about to touch, a subject cramped against an edge, a heavy mass unsupported on one side. It keeps a picture from settling, which is why it holds attention. Composition guidelines mostly resolve tension, so producing it usually means breaking one deliberately.
Examples in practice
Placing a subject tight against the frame edge they are walking toward makes the picture feel restless and unresolved.