The map sending an element x to g x g^{-1} for a fixed invertible element g in a group, ring, algebra or similar context; describes the action of an element by inner conjugation and yields an inner automorphism when g is fixed.
The operation that sends an element x of an algebraic structure (typically a group or a group-like object) to its conjugate g x g^{-1} by another element g, describing the internal symmetry action by inner automorphisms.