why we use $variablename in javascript code example

Example: how to name a javascript variable

//variables can include any letter, any number, or the underscore
	//NO SPACES!!! USE UNDERSCORES!!!
	//variable names are case sensitive
	//example:
var change_this = 'whatever you want here'
	//change_this is a variable (change it to your variable name)
	//'whatever you want here' is a string (you'll learn about this later)