If you want to make games in Flash, you'll want to study ActionScript. Usually Flash is limited to 2d graphics but there are 3d engines out there such as Papervision3D and others.
There's some pretty good libraries as well, such as Erin Catto's Box2D physics engine ported to Flash.
I'm going through this book http://www.amazon.com/Learning-ActionScript-3-0-Beginners-Guide/dp/059652787X and I'm really liking it.