Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict the geometry of molecules based on the repulsion between electron pairs in the valence shell of atoms. It posits that electron pairs arrange themselves to minimize repulsion, influencing the molecule's shape. The theory distinguishes between bonding and lone pairs, with the latter exerting more repulsive force, significantly affecting molecular geometry and resulting in structures like linear, trigonal, tetrahedral, and others.