How many time did you start editing an $identifier or a command, forget about the syntax, check it, and get back to the code? Too many time? This is perfect for you then! A calltip is a little text poping up when you are editing an $identifier, it displays the syntax of that $identifier, it even highlights which parameter you are editing if there are more than one syntax for the same identifier, you can go through them using the up/down arrow key (or by clicking on the arrow on the calltip itself), you can make it disappear by hitting the escape key.