An “avatar” is an image that represents you online—a little picture that appears next to your name when you interact with websites.
A Gravatar is a Globally Recognized Avatar. You upload an image and create your public profile just once, and then when you participate in any Gravatar-enabled site, your Gravatar image and public profile will automatically follow you there.
For example, once your Gravatar account has been set up then your image will automatically appear on OpenAI, Slack, WordPress etc.
Gravatar is a free service for site owners, developers, and users that is run and supported by Automattic. Your Gravatar URL is automatically reserved with every WordPress.com account.