What’s the difference between Microsoft Security, MSRT and MSERT?

What’s the difference between Microsoft Security (Windows Defender) / Windows Malicious Software Removal Tool (MSRT) and Microsoft Safety Scanner?

I’ve been looking at the Microsoft articles on these tools and some posts I googled. I’m still confused about when I should use these in real case scenarios (for a computer repair technician).

I've read a old post you have here on this subject but doesn't really say much.

I’d love to hear opinions on when to use these tools. My assumption was that Windows Defender was enough.

Any advice much welcome