Hotlinking is when someone displays your images (or other media) on their website by directly linking to your website. This means that they get to display your files while using your bandwidth (this is theft).

Setup of Hot Link Protection
1. Log into cPanel
2. Go to Hot Link Protection

Fields
URLs to Allow Access- Enter the URLs you want to give access to the restricted files. Make sure you enter these with and without the www's if you want the images to be accessed both ways.
Extensions to Allow- Enter the file extensions you want to block access from sites not listed in your URLs to Allow Access list.
URL Redirect- If you don't have direct requests enabled, by entering a URL here this will redirect people if they enter the URL of the file directly into the browser.
Allow direct requests- Check this if you want to allow people to be able to access restricted files by entering the path/URL into the browser.

If the images are uploaded in the correct location and you coded references for each image correctly, you have Hot Link Protection enabled. You need to add your domain/subdomain to the URLs to Allow Access list found within Hot Link Protection. You should specify both with and without the www's if you want the images to display from both URLs. You do this through the 'Hotlink Protection' section of the control panel.