Wondering what I mean by "tags"? Well if you look on the right hand side of the main screen you'll see a section with the most popular tags listed. They appear in different sizes and boldness.
A tag is basically a keyword, used by the search function to help locate posts and threads on a particular topic.
So, when you're posting a new thread, you can add keywords, or tags, that you think might be helpful for people looking for your topic. For example "grooming" and "braiding" on a thread about braiding your horse for a show, or "horsemanship", "Percheron" etc. etc. - you get the idea. You can add tags to your photos that you upload too.
You can tell the most popular tags, in other words, the hot topics of the day, but the size and boldness of the font in the tag box. And if you click on one of those tags, it will take you to a page with the relevent threads and photos
Pretty kewl if you ask me :)