The addition, modification, or removal of anything that could have an effect on IT services. The scope should include changes to all architectures, processes, tools, metrics, and documentation, as well as changes to IT services and other configuration items.
Change is the primary cause of incidents but also the vehicle for improvement. Balancing the speed of change with the stability of services is the main challenge of IT management.
We believe change should be boring. By making changes small, frequent, and automated (via CI/CD), we reduce the "blast radius" of any single failure. If a release is a risky event, you aren't doing it often enough.