What is meant by "Endpoint Server?"

I was looking over the installation steps for installing DLP 11.6 in a 2-tier setup.

I read ahead through the documentation to see how to set up the endpoint DLP agents for Endpoint Discover and Endpoint Protect and saw that it said:

"Before you begin, make sure that you have installed and configured an Endpoint Server."  No further explanation seen before that.

I had never heard of "Endpoint Server" before.  Our package includes Enforce Server, Network Monitor, Network Prevent For Email, Endpoint Monitor and Endpoint Prevent.  No "Endpoint Server."

Is another new separate server hardware and license purchase needed for "Endpoint Server" of does this mean the Enforce Server?