User management is an essential part of any business application. Microsoft Dynamics CRM 2015 provides out-of-the-box support for user management and security. If you are using Microsoft Dynamics CRM 2015 on premise, a user can be added to Microsoft Dynamics CRM 2015 after being added in Active Directory. In the case of Microsoft Dynamics CRM 2015, online users can be managed using Office 356 portal.
Access to the Microsoft Dynamics CRM 2015 application can be managed using an entity called Security Role. Once a user is added to Microsoft Dynamics CRM 2015 he should have at least one security role or should be part of the owner team (the owner team should have at least one security role assigned). User security is handled in Microsoft Dynamics CRM 2015 in three ways:
Role-based security
Record-based security
Field-level security
Note
You can refer to https://msdn.microsoft.com/en-us/library/gg309524.aspx to get more information about the CRM 2015 security model.