Please look around since there are many topics on this.
The Floof-O-Meter is like "Karma". When you do something good or whatnot, another member can "nuzzle" you to show their appreciation. You can start nuzzling people once you have hit 25 posts.
It doesn't change your forum experience at all, so it's not really all that crucial. But, it's a nice little meter thing. :)
To nuzzle, when you hit 25 posts, you will see the word "Nuzzle" (as a link) under someone else's Floof-O-Meter, and you can nuzzle them for doing something good/appreciation. Some people take this way for granted. You cannot nuzzle yourself, however.