HotLink Protection prevents other websites from directly linking to files on your website.
HTML code can call images from anywhere on the web. HTML <img> tags allow you to display an image at any URL you chose. However, when an image is called from an external website, that site's bandwidth is used to transmit the image. A web browser pulls down your static HTML and when it attempts to load the given image, it makes a request to the image's host server.
When others link to images you have on your website, it uses your bandwidth to transmit the image.
By enabling Hotlink Protection, you can define which URLs are allowed to access your images. This prevents unwanted linkers from using your bandwidth to display your images on their site. For those sites which do not have access to link to your images, you can define where they should be directed.