Avatars are the pictures underneath your user name when you make posts.
Custom avatars are enabled on this forum, which allows you to upload an avatar image from your computer.
After you have registered, you may set your signature. This is a piece of text that you would like to be inserted at the end of all your posts, a little like having headed note paper.
You will then have the option to include your signature on any posts you make. If you have specified a signature, then the forum will automatically append your signature to any messages you post. You can disable signatures on a per-post basis by un-ticking the 'Show Signature' checkbox when you compose your message.
You may turn the signature on and off on posts you have already made by editing the post and altering the state of the 'Show Signature' option.
You can set your signature by going to your Edit Signature
section of your User CP
These small images are called Avatars. They are displayed below your username on all posts that you make. There are two kinds of avatars: those provided by the administrator and those that you upload yourself.
For more information on how to upload your chosen avatar and signature, you can read the Avatars, Signatures, Images FAQ