Let's Control It

Hi,
What exactly is ment by Controller IP or Controller itself?
In some examples it has LAN IP, in others WAN IP.
Is the controller the esp device where espeasy is running or is it the Windows pc which is used with browser to configure the system?
Trying to configure the first tutorial, but the info on that point is a bit confusing

Controller is the device receiving the data from the sensor.

This could be domoticz, openHAB,...

TKS tamunave,

Yes I got the Domoticz tutorial work now with virtual switches.
Controller IP in my case 10.0.0.15, Windows PC where the Domoticz software is running in background.
Originally thought the Domoticz server is somewhere in WEB but it seems to be on my own LAN without any connection to outside.