In case of commands, commands never return anything, so the execute function returns nothing. Then we have the function name. In parens, we have the argument list. Each argument is separated by a comma. The name is internal to this function and is what you will use to refer to the data that is contained within this argument.
Good names are typically nouns.
After arguments we have the code. After that, we have a single argument surrounded by parens. When a variable is used like that, it is replaced by its current value. The backslash is a special character, an escape code. When this function runs, whatever is within the parens will get calculated first .