I know how to use/code sending and registering objects in mvvm light. This is not what I want to ask but I am curious what is happening behind the scenes? I was searching all over and I couldnt find a deep explanation. Is it like address pointing in the memory. objects are addressed somehow by type or? I mean how one class sends and others finds it just by indicating their type. Can somebody shed some lights here please or a link reference where I can read about it?
I think the below links will help you to understand how register/subscription works in mvvm light.
https://msdn.microsoft.com/en-us/library/ff921122.aspx
http://brentedwards.net/2010/04/13/roll-your-own-simple-message-bus-event-aggregator/
I guess Mvvm light also using similar implementation. You can see the mvvm light messenger code here
Hope it helps