You and the Overseers are the only ones that can edit your account and profile information. If you're an Overseer, you will always have tabs. If you're a user, you only get tabs on your account :)

Tabs

View: shows what your user profile looks like
Edit: edit account/profile information
Messages: private messages
File Browser: lists all the fics and art you've uploaded to RP. You can delete and rearrange them at will, though deleting a file may not delete the node it's attached to (so edit/delete whatever you attached it to first) and I have no idea if it will break if you move it into a different folder after attaching it :)

Account

Located under the "Edit" tab.

Email address: change your email address
Password/Confirm password: change your password
Picture: your avatar. If you're replacing it, do not check the delete box as it has been known to upload and then delete your newly uploaded avatar :) Just upload a new one and it will automagically replace the default one or any you were using previously. Unfortunately due to the module being used to resize images, animated avatars no longer animate :(
Signature: anything you want to appear at the bottom of your forum posts
User title: changes depending how many posts you've made (not just forum topics but art, fics and wiki pages too). Or you can completely override it and make your own :)
Locale settings: set your own timezone
Private message email notification: tick to get emails when someone messages you. Untick to come check at the site. The "Messages" box in the right column should tell you if there's any new ones as they come in

Profile

Located under the "Edit" tab. All fields are optional.

Name: Your real name, or whatever you feel like going by
Gender: think there's enough options to keep most people happy
Date of birth: not shown on your profile, just used to calculate your age which is shown on your profile

Fan Character Bios

add a fan character bio in the "You" block. Included here as it is as the name suggests a profile type :)

Picture: upload a picture of your character. It will get resized to 300x300 px so mug shot might be best

Most of the stuff is pretty straightforward, leave out whatever doesn't apply. Just because I've been asked before, "Personality" is what your character is like "on the inside" and "Demeanour" is how they carry/express themselves to others.

Your profile will show an enlarged version of your avatar if it can, some basic information from your account, any profile fields you filled in, your latest artwork, fics and a list of your fan characters with links to their bios.