Gravatar is a service built and owned by Automattic, the same company that owns WordPress.com.
Gravatar allows users to associate a user profile and avatar with their email address.
Having a WordPress.com account helps with security and authentication. It verifies that you are the rightful owner of the email address associated with your Gravatar.
If you want to use Gravatar, you are required to have a WordPress.com account, but it does not require you to have a WordPress site, or use any other services from WordPress.com or Automattic.
By linking your Gravatar to your WordPress.com account, you ensure that your chosen avatar and profile data appear consistently across different websites and services that support Gravatar, including WordPress.com.
Gravatar is free to use. Please learn more at https://automattic.com/privacy
Gravatar Support 