If you've ever seen a green dot on someone's Facebook profile picture, it means they're currently using one of Facebook's many services. This could be anything fromChat to Messenger to even just browsing the news feed. The green dot is a way of indicating that the person is online and available to chat or message.
There is a service that you can sign up for that will put a green dot on your Facebook profile picture. This is supposed to indicate to your friends that you are available to chat. I'm not sure how effective it is, but it's a thing.
As more and more people become aware of the importance of sustainability, companies are beginning to offer green dot on facebook profile picture services. This is a great way to show your support for sustainability, and it can also help you save money.