Recording game/computer/tv screen on camera

How come when you use some cameras to video record say the tv, it comes out with lines or other things everywhere? And how do you go about fixing it, or what type of camera/specifications are needed to record without those problems.

i remember asking myself the same thing a good while ago, if i remember correctly this is why:

http://en.wikipedia.org/wiki/Raster_scan

our eye picks the thing as a continuous flow, but the camera picks the variations of the screen.