What are the user types in sap

List R/3 User Types
Dialog users are used for individual user. Check for expired/initial passwords.  Possible to change your own password. Check for multiple dialog logon 

A Service user - Only user administrators can change the password.  No check for expired/initial passwords. Multiple logon permitted 

System users are not capable of interaction and are used to perform certain system activities, such as background processing, ALE, Workflow, and so on. 

A Reference user is, like a System user, a general, non-personally related, user. Additional authorizations can be assigned within the system using a reference user. A reference user for additional rights can be assigned for every user in the Roles tab.  

What is a profile and how many types of profiles are avail

A profile in the Sap system is an OS file contains parameters and configuration information of the SAP Instance.

The profiles are located under /usr/sap//SYS/profile

There are three types of profiles available in SAP

1. Start profile: defines the Sap R/3 services to start (different start profiles for different instances).

2. Default profile (system profile): this contains parameter values used by all application servers from the same SAP system.

3. Instance Profile: contains Instance specific parameter values like how many types of work process to be started for an Instance, default logon language, shared memory details etc..  (Different start profiles for different instances).