T-SQL - What is an inline-view?

Question

I recently answered this question how-to-call-user-defined-function-in-order-to-use-with-select-group-by-order-by

My answer was to use an inline view to perform the function and then group on that.

In comments the asker has not understood my response and has asked for some sites / references to help explain it.

I've done a quick google and haven't found any great resources that explain in detail what an inline view is and where they are useful.

Does anyone have anything that can help to explain what an inline view is?

Answer 1

From here: An inline view is a SELECT statement in the FROM-clause of another SELECT statement. In-line views are commonly used simplify complex queries by removing join operations and condensing several separate queries into a single query.