$tag object description

Hi,
im working around with tags lately and i can’t seem to find the $tag object description. Only thing i’ve found so far is the $post object description in a forum post (it doesn’t say where the user originally found it) $post object description
So, you know where the user found the description of $post? Maybe i can find the description of $tag there 🙂

(only variable i found is $tag-name, which is the name of the tag (no kidding), i made this post to try to find out how to get $tag-ID )