jQuery is already built into Drupal, you can use it instantly with no modification. If you use any other type of Web site, you may have to download and install jQuery.
Download jQuery from jquery.com. You can choose an unreadable
minified version with all whitespace and comments removed or a larger human readable version. Download the small minified version for use on your Web site and the full version when you want to read the code.
Browse the starter tutorial for non Drupal users at docs.jquery.com/How_jQuery_Works. After you finish the starter page, you can return to learn more.