Describe the activity of protons when an acid and base are mixed together

In acid-base reactions, proton (H+) moves from acid to base, meaning that the acid is a donor and base is acceptor of that proton. This happens because of the difference in potential energy (proton goes from higher potential energy to a lower potential energy).

So, definition can be: an acid is a molecule (or ion) that can transfer a proton to another molecule and a base is a molecule that can accept a proton.