In SAP systems, when an ADMINISTRATOR creates a new user ID, he has to specify the TYPE of user this user ID should be assigned to. Users in a system can be categorized according to their purposes. This allows different security policies to be specified for different types of users. A security policy may, for example, specify that a human user (end-user) who executes tasks interactively needs to change their passwords regularly, whereas this requirement does not apply to users who are running jobs in the background. Following are some types of users in SAP:

• System user: Users with this user type can perform certain system activities such as background processing, ALE (Application Link Enabling), workflows, etc. The system user does not allow interactive access to the system. When a user has the service user type, the system won't check for expired/INITIAL passwords, only a user administrator can change the password, and multiple logins are allowed.
• Dialogue user: Dialogue users represent human users, also called end-users. This user type is needed for INDIVIDUAL, interactive sessions in the SAP system. When a user has dialogue user type, the system checks their expiring or initial password, enables them to change their passwords, and checks for multiple logins.
• Service user: Service user types generally represent a larger user community and allow. This user type facilitates guest access, or the ability to connect to REMOTE systems with certain rights. When a user has the service user type, the system won't check for expired/initial passwords, only a user administrator can change the password, and multiple logins are allowed.
• Communication user: It enables dialogue-free interaction or communication between systems. Dialogue logon cannot be done with this type of user.
• Reference user: Rather than assigning roles individually to each user, a reference user is created to hold a selection of roles that are to be assigned to a larger group of users. If you need to create a large number of users in your SAP system with the same authorization assigned, you can use this method.