To Understand the differences between intrinsic and extrinsic motivation, we must first understand what each of them actually are:
Intrinsic Motivation: Intrinsic motivation comes from within. Our feelings and our desires are what drives us t achieve something.
Extrinsic Motivation: Extrinsic Motivation comes from outside sources, generally in the form of someone else holding us accountable.
Now neither of these sources of motivation are wrong per say, however we do find Intrinsic motivation will be more sustainable long term compared to Extrinsic motivation.
Saying this though, it is important to understand that for a lot of people, particularly when it comes to achieving health and fitness goals, such as weight loss for example, that we begin with Extrinsic Motivation. This is where a good coach is highly beneficial to allow you to discover what it is you enjoy doing, what you desire and how that will make you feel. In essence you learn how to understand and intrinsically motivate yourself by utilising Extrinsic Motivators to begin with.