Can anyone explain the difference in it? Also which one is more popular now. I was just looking on another site and saw this post and it got me wondering.
This is MS C++ which still runs on .NET, I'd recommend learning proper unmanaged C++ instead of this. It's basically an unnecessarily complicated version of C#.
C++ is far more common than Managed C++. It may be the industries I've worked in (a mix of defense and small tech companies) but I've never seen anyone using Managed C++.
C++/CLI isn't too common. Typically when we're talking .Net framework, companies implement in C# rather than managed C++. One of the reasons is you're essentially defeating the purpose of a C++ app by robbing it of its performance benefit. The syntax of managed C++ is also different in some areas than unmanaged. An additional factor is the resource pool. There are vastly more C# programmers than C++ or C++/CLI programmers.