what does declaring $ before variable in js code example

Example 1: how to write a variable in js

//choose the best for your solution
var myVariable = 22; //this can be a string or number. var is globally defined

let myVariable = 22; //this can be a string or number. let is block scoped

const myVariable = 22; //this can be a string or number. const is block scoped and

Example 2: how to add a variable in js

var x = 5;         // assign the value 5 to x