Joplin cloud/server - Do you need to share your email address to share notes with other users?

For Joplin Cloud/Server, to share notes with other users. Do you need to signup with an email address and share that email address to those you want to share notes with, or does Joplin Cloud/Server allow you to set a username that can be different from your email address for your Joplin account, or does Joplin generate some sort of ID to use when sharing notes with other users?