Will my package arrive today?

I recently ordered a Logitech Extreme 3D Joystick. I chose overnight shipping. But I want to know if my package will arrive today. I ordered it yesterday between these hours : 1 - 4:00 PM. The place I ordered from was Pennsylvania. Now the package is in Transit, does that mean I will get the package today? The estimate says today the 25th. Will my package arrive today? And what does Transit mean?