What is User Testing?

The latest Testing Glossary video is here: https://youtu.be/i8XeMiWfc2A?si=eTggAI7qtRUsROW9

What is user testing? Is it just the users checking and accepting the system? It can be, but what users test and how they approach the challenge needs some consideration.

So how do users actually approach testing? What are they trying to achieve? How do they satisfy themselves that a system actually works for them?

This video explains...