The SAP system categorizes users into several types which are Dialog, System, Communication, Reference and Service. Each user type has their own function and purposes.
You can assign and change the user type by using transaction code SU01. Switch to Logon data tab. From here, you can assign or change it accordingly – once done, click on Save to apply the change.
You can get the overview of the usage user type as following,
Dialog
Individual, interactive system access.
System
Background processing and communication within a system (such as RFC users for ALE, Workflow, TMS, and CUA).
Communication
Dialog-free communication for external RFC calls.
Service
Dialog user available to a larger, anonymous group of users.
Reference
General, non-person related users that allows the assignment of additional identical authorizations, such as for Internet users created with transaction SU01. No logon is possible.
