The users listed here are your application users, the one who starts a conversation from your application will be shown here. You will see the Start conversation button if the user hasn't started any conversation yet, you can use this button to start a conversation with your users.
You can see the information such as the user's last seen time, and the latest conversation assignee. Also, there is a search option to search the user with email ID and user ID.
Note: All the users with pseudonyms (Such as Fancy Shark) are anonymous.