ITIL : Change Management and Release Management Overview
A Change by definition is any modification to a managed environment, including the addition, removal, or replacement of any component (Configuration Item) supporting the infrastructure or a service in that environment.
All modifications require an authorized Change Record, and must be logged in a central repository where it can be tracked and audited.
The goal of the Release Management process is a successful release of a set (or sets) of planned changes that releases at the right time, does not negatively impact customers and users, that delivers the business value it was designed to address, and does not cause an inordinate impact on user support teams.