What is meant by Understanding?

When we say we understand something, what does it mean? Does it mean that we have an intuitive feeling of what that concept/object is?

Does it also mean that we understand the mechanism of how it works? But then is it the mechanism that we are ‘understanding’ or the ‘concept’? And is there a difference between the two?

Can ‘levels’ of understanding vary? With one person understanding a concept upto a certain extent, and another to a far greater amount?

How does one increase this ‘understanding’?

Is understanding something central to intelligence? Is it central to consciousness?

And does AI ‘understand’? Could AI ever understand?

Or is understanding just a ‘feeling’ we get that we are ‘familiar’ with ‘something’ and can manipulate that ‘something’ in our minds (or with our tools) to varying extentes?