There is always at least one user in the system - Administrator. If necessary, you can add more users. This lets you see who created a record, protect your own records from changes and hide from other users (see access rights). It makes sense to set a password for each user.
The administrator account has a special status. Only the administrator can create and delete other users. Also the administrator can see all records (including hidden ones), edit records protected from changes and change the owner of a record. The administrator account cannot be deleted.