Author Bio is a small section at the end of the blog posts, where you can display information about the post author with links to their website and social profiles.
By default, WordPress makes available only the website field. If you want to display other links to your social profiles (eg. Facebook, Twitter) you need to add them via your Gravatar profile.
Gravatar means Globally Recognized Avatar and is your personal online avatar that follows you across the online world. Is a simple and free global service that integrates seamlessly with WordPress.
Get started by going to Gravatar’s website.