Hz refers to the refresh rate. The number means how many times the picture is broken down and rebuit in one second. Your most common are 60, 120, 240, and 600. The higher the number, the clearer and smoother the picture will be, especially with gaming and action movies. Plasmas have the best at 600Hz and are ideal for gaming and movies, but you have to sit straight away or you lose the picture. Some of your LED tvs are going up to 240Hz which look incredible, but are still very pricy. For the money, an LCD 120Hz is really good and becoming very affordable.