Why use TAGS?
 

When I make a post in my forum I see the option to add tags, what is this for? What are the benefits of adding tags?

The basic theory is that it's a way to find subjects the keywords of which don't appear in the post.

e.g. A post about 1967 Impalas may never mention the word "Chevrolet", so add it as a tag and the post is included in a search for "chevrolet".

But don't feel bad if you don't use them either. Nobody does. Too much effort I guess.