An expression that instructs a program to leave a subroutine and go back to the return address. The return address is where the subroutine was called from.
Instead of relying on the last expression in a function code block to produce the right value, you can also explicitly specify the result using a return expression. When the return expression is executed, it will exit out of the function's code block immediately. This means if you place the return expression before other code, the code that follows won't execute.