Just wondering what the purpose of tags are, and how do you use them??

Book tags are words and short phrases that you put in to describe a book. The less personal your tags are, the better for other members to use. For example words like Paris- the location the book takes place in, Modern day Fiction, or Historical Fiction would allow more club members to find that book.  This allows you to search for a book by a tag word that you might be interested in. If you go to the Help Center and search for "Book Tags" There is a whole page devoted to Tags and how to use them.

Hope that this helps.

Since book Tags aren't searchable, I don't find them very useful for the club Tags unless they show up in the Club Tag Cloud.  I use them for personal Tags and I keep lists of books on my TBR that are WLed and on my BIR that are WLed.  That way I can easily see on another member's list and I can bring up a list of what I have available for games or the WL Multiples thread.  The only club use I use them on is to Tag series and to Tag other copies of a book when I see that an obscure unlinked version exists like a foreign copy gets posted or something. 

You can search for books with a certain tag if the tag is in the Club Tag Cloud
Or you can apply the tag to one of your books, then go My Tags to search the tag. You can apply it to a book that doen't fit the tag - jus remember to remove it.

I don't see the point of tags.  I have them turned off so I don't have to see them.