Tags are search terms that can be added to topics. Tags make it easier to find topics on certain subjects if the tag words are used wisely. They are an alternate way to search for information, as they will only show topics if the word you are looking for was used as a tag.
You can show the tag box at the top of the forum, but it will not show up until there are 6 different tags in use in the forum.
And since we have about 95% dumbassedry on this board, I don't want to rely on people tagging their posts.