Movies uploaded to iTunes
I don't believe there is any such thing as "uploading" to iTunes on the Mac. Rather, you import/add your own video files to your library or purchase them from the iTunes store.

Any movie or tv show purchased from the iTunes store should automatically be in your Mac iTunes library and also be able play on your iPad after you sync it there. 

You can import pretty much any movie file of your own to your Mac iTunes library. From there, you can use iTunes to sync it to your iPad; however, your iPad can only play a few specific movie formats (scroll down to TV and Video). If your movies aren't in that format, you won't be able to play them on the iPad whether you sync them or not.

Once your iPad is connected to your Mac, you have options in iTunes on the Mac to auto-sync certain playlists of videos or all videos to your iPad. You can also use it manually, and simply drag/drop the desired video files from your Mac iTunes library onto your iPad library when it is connected to iTunes.