What is "Orion agent server"

I stumbled upon this article:

https://support.solarwinds.com/SuccessCenter/s/article/How-to-Setup-HTTP-HTTPS-Monitor-in-SAM?language=en_US

And this statement got my attention:

Please note the behavior of HTTP/HTTPS monitors in Server & Application Monitor.

• The agent managed nodes will be attempting to reach the website from the Orion agent server
• Non-agent managed nodes will be attempting to reach the website from the Orion polling server (this applies to external, ICMP, SNMP, and WMI managed nodes).

And I can't just figure out what exactly Orion agent server is.

Is it the server that manages agent deployed on specific node? Then how is this different from "Orion polling server"? Or maybe this refers to the server agent is deployed on?

Please help me understand!