What do you know about change management?

Change management is actually the set of processes used to manage the people side of change, and using organisational tools to engage and utilise the people (by people we mean individuals and teams, it may well be on the whole organisation level) to ultimately achieve the required business outcome, be that a strategy, structure, system, skills, and many others.
Change management cannot be described in seperation from project management, as changes happen as a result to projects/programs initiation.
There are many theories about change management, most famous one is the kotter8 step change model (good to start from it).
Change management can be simplified into three main steps: (1) Start change (2) Manage it (3) Ensure it sticks

It is the most missed ingredient in implementing changes and missing it the main reason behide failing to achieve desired results.

The best change management is the parallel change over system.