Managing your avatar profile image in WordPress.
The default for managing your avatar in WordPress is using a gravatar. This means you need to sign up at gravatar.com and add some avatar images to your new account. The e-mail address you at gravatar.com and for your WordPress sites will link the avatar image from gravatar.com to your sites.
The process is a bit cumbersome for users that just need to make some posts on occasion or need to be a part of a site. So various plugins are created to fix this cap.
An example from WP user Avatars.
It is being worked on adding an avatar feature into WordPress so the user can upload and use their own image without having to sign up at gravatar.com.