What do we mean when we write usernames of someone in the documentation?

Let me elaborate. I was reading through the Governance page of an MDN project . There, under the Peers heading, we have mentioned some peers. In front of their names, there are usernames IDs.

My question is, what do we expect these usernames? Are they Twitter profiles, or GitHub profiles or Mozilla profiles?
I tried to find answer to this, but didn’t find it anywhere.
Please help.

Thanks :slight_smile: