Change is quite simply defined as “make or become different” or “the act or process through which something becomes different”.
There are a thousand different models of change you can find, and many have substantial fan clubs behind them.
We prefer to think of change as a natural part of business and life. Living things (like people) change all the time. That’s part of how they survive. Businesses (which are really just lots of people together) are the same. They change all the time.
Without oversimplifying it, “change” in a business sense means “making your business, or part of your business, different than it was or than it is today.”