What is managed and unmanaged code?

Managed code is code which runs inside the boundary of CLR.
The application which is created from.Net framework language is Managed code and if application not created from.Net framework languages is called Unmanaged code.
Unmanaged code is code which does not run inside the boundary of CLR like you call hangout from the .net code the hangout application is unmanaged code because its resource allocation, utilization is not handled by CLR.