There are lot of threading model available, but we focus on 
threadingmodels that are common to win32based environments

singleThreaded:There is only one thread with in the 
process,and it is doing all the work for the process.The 
process must wait for the current execution of the thread 
to complete before it can perform another action.

Apartment Threading (Single Threaded Apartment)
Apartment threaded means there are multiple threads within 
the application. In single threaded apartment (STA) each 
thread is isolated in a separate apartment underneath the 
process. The process can have any number of apartments that 
share data through a proxy. The application defines when 
and for how long the thread in each apartment should 
execute. All requests are serialized through the Windows 
message queue such that only a single apartment is accessed 
at a time and thus only a single thread will be executing 
at any one time
Free Threading (Multi Threaded Apartment)
Free threaded applications were limited to programming 
languages such as C++ until the release of Microsoft .NET. 
The free threaded/Multi Threaded Apartment (MTA) model has 
a single apartment created underneath the process rather 
than multiple apartments. This single apartment holds 
multiple threads rather than just a single thread. No 
message queue is required because all of the threads are a 
part of the same apartment and can share data without a 
proxy.

The developer must provide thread synchronization as part 
of the code to ensure that threads do not simultaneously 
access the same resources