Read-Only Domain Controller (RODC)

Receives replication (one way), does not store login information, authenticates via the main D.C.
May only carry local credentials for immediate staff, no admins
Used under specific circumstances
Can also perform DNS

Scenario

A smaller office with less employees may find it is slow to log in due to having to authenticate with the D.C from another site

How to setup: (would normally be done via RDP or install locally and ship it to the location)

On a Domain Controller
Active Directory Users and Computers
Right click Domain Controllers > Pre-create a read-only Domain Controller account
Specify User/Group to be able to log in
Finish
Right click > Properties > Password replication policy
Allowed RODC Password Replication Group
Add local users' credentials to this group (non admins)
Log into the other server
After installing ADDS, when promoting the server to a D.C., Tick "RODC"
Complete Setup