What is a molecule called that a protein binds and what types of interactions occur to create this binding?

Ligand

Explanation:

A molecule that a protein binds is called a ligand. The word comes from Latin ligare, which means to bind. In order for a protein to bind to a ligand a non-covalent bond is necessary. Non-covalent bonds are weak, usually weaker than covalent bonds and are thus commonly reversible.

The substrate is a type of molecule that can bind to a protein, in this case enzymes type proteins. They can also be called cofactor, which can be a metal, a prosthetic group, smaller molecules (coenzymes)

Explanation:

Enzymes are proteins and biological catalysts, which serve to accelerate chemical reactions. Enzyme-substrate binding can occur through two models, the induced fit model which conforms to the shape of the active site (site where the binding occurs) and the lock and key model, a perfect fit of the substrate at the active site. Non-covalent chemical forces, ionic bonds, H bonds and Van der Waals forces participate in the substrate binding to the active enzyme site.