I nice factoid: in Erlang, `_` if functional. It means "I don't care about this variable". When pattern matching you can put `_` to not bind value in function or pattern to anything or prepend a variable with `_` to tell compiler that you won't be using it, but it's there for "documentation" purposes. For example `[A|_]=List` will extract first element of list into A and ignore rest of list. Underscore has some other uses too.