Difference between Async and Sync events

[Lenfors]

Hello!

I really need to know what the difference is between asynch and synch events!

For instance, I created a new application with only a TIWTimer on the form. Then I created a OnTimerEvent doing nothing.
When run the OnTimerEvent is fired as it should.
Now I added a OnAsynchTimer event to the same IWTimer.
When run now the OnAsynchTimer is fired but not the OnTimerEvent?

Another example:
New empty application with only a event defined for OnResize doing nothing.
When starting the application or resizing the browser window OnResize  is called as expected.
Now creating a OnAsyncResize event. Both OnResize and OnAsyncResize  are called on form creation and browser form resize.

Now I added a IWTimer to the last example and added a OnTimer event to it.
The OnTimerEvent fires as expected but also the forms OnAsyncResize event?!
If I remove the OnTimer event and instead add a OnAsyncTimer the OnAsyncTimer is triggerd as expected but there is no OnAsyncResize triggered.

Is there some documentation about this? I Googled but can't find any good explanation.

Best regards, Mikael