not defined error in javascript code example

Example 1: $ not defined error

<script src="http://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<script type="text/javascript" src="./javascript.js"></script>
<script
    src="http://maps.googleapis.com/maps/api/js?key=YOUR_APIKEY&sensor=false">
</script>

Example 2: not defined javascript

/* Means something was not defined for example you wanted to print */ "X"
/* but X is not defined to defined you have to make a variable for it */
X = "Something" /* Once you define it it'll print the value successfully */