someone explain how different Authorization, Authentication, Roles, and Mitigationare, and also how different for Small, Medium, and Large businesses?...

Can someone explain how different  Authorization, Authentication, Roles, and Mitigation are, and also how different for Small, Medium, and Large businesses? If you can compare four attributes that are critical in enterprise systems today, that will be great, also if you can tell me what steps can be taken to mitigate threats for small, medium, and large hospital enterprise systems.