What exactly is msnp24 in relation to Skype

I was having a strange problem with my Skype where I could use 1-1 conversations normally, but I could not take part in, or even see, group conversations.

Following the accepted solution in this article, I was able to solve my problem very easily.

I quote the answer here in case it vanishes or is edited.

After struggling a bit, I found some useful commands. You can type these in any skype chat window.

/dumpmsnp – show details about your connection
/showplaces – show where you are currently connected

What was happening was that /dumpmsnp command was showing "LoggedOut", but I was online and talking almost normally (except group chats).

System: MSNP: Connection Data:
* Status: LoggedOut

To solve this "LoggedOut" issue, try this on any chat window:

/msnp24

and restart your Skype.

After restarting, /dumpmsnp output shows the following status:

System: MSNP: Connection Data (MSNP24):
* Status: LoggedIn

I don't know exactly why, but the /msnp24 command kinds of converted my account to this protocol and now everything works perfectly.

A pet hate of mine, however, is solving a problem without understanding how it was solved. So I am very curious what was actually going on behind the scenes.

My question is this: Can someone please explain what exactly was happening, why Skype behaved in this way, and why typing /msnp24 followed by a logout/in cycle fixed it