There are two kinds of players. A permanent account, an account that is there, and when you log off or leave a server, is still there, unless banned or removed from ROBLOX forever. There are over 60,000,000 accounts on ROBLOX. These accounts must be created through the registration process and accessed through the login process. These accounts may interact with the community depending on the set chat settings and safety measures in effect on the account. These accounts can also be banned by the ROBLOX Moderation and Administration Staff as an act of punishment against the player using the account.
Then there are Guests, players who do not have an account, an individual name, and are present only for being inside the server. Once outside of the server, the Guest does not exist and cannot interact with the community. This is the only option to playing on servers while not logged in when accessing and during the extent of the playtime. Guests cannot communicate with other players without the use of certain scripts or exploits.