The Guest Account is a Windows Default Local User Account.
Guest account
The Guest account is disabled by default on installation. The Guest account lets occasional or one-time users, who do not have an account on the computer, temporarily sign in to the local server or client computer with limited user rights. By default, the Guest account has a blank password. Because the Guest account can provide anonymous access, it is a security risk. For this reason, it is a best practice to leave the Guest account disabled, unless its use is entirely necessary.