Blue Ray High Definition Ok, At A Bargain Price How To Make My TV High Definition For Viewing Movies?

How to make my TV high definition for viewing movies? - blue ray high definition ok, at a bargain price

OK, I have a PS3 and some blue rays, and I know how I change my TV in HD. I have a big 50-inch screen that says HD compatible, but I'm not sure what I need to high-definition version. Note that I did not see the TV shows in HD, just my blue ray and games. What do I need cables or connections?