Random function

What does the tutorial mean by this note below? What is meant by function calls? Are they different from the Math.random() function call?

Note: Like Storing Values with the Assignment Operator, all function calls will be resolved before the return executes, so we can return the value of the Math.random() function.

Challenge: Generate Random Fractions with JavaScript

Link to the challenge:

What it is saying is, before a function will return a value, if we provide a function to be evaluated in that return, then the return will wait for the evaluation of that function.

return Math.random() would evaluate the random floating-point number function, and then return the result of that function call.