Let expression

Let expressions are a way for people to do something called "variable binding" in a computer program. Basically, it allows you to give a name to a value that you want to save and use later. For example, if you want to save the number 3, you could give it the name "x" and write "let x = 3". Later, if you want to use the number 3 again, you can just type "x" and the computer will know that you mean the number 3.