Hotlinking is when you are directly linking to another site’s graphics, files, video, etc. instead of linking to those items from your own server.
For instance, when I share a graphic like this one
I encourage you to right-click it and save it to your computer and either insert it into your blog from your computer or upload it to your account at PhotoBucket and use that code.
This is important because every time an image is viewed on a page on the web, it’s pulling bandwidth from wherever it’s stored. If all the Blogging Basics 101 readers used that graphic (great!) and used my URL instead of downloading it to their own computer/server (not so great!) then I would have a bunch of bandwidth being used and things could get expensive for me (definitely not great!).
If you need to know how to put a button on your sidebar without hotlinking, I have those instructions for you already.