Audio and video compression format developed by MPEG group back in 1993. Official description: Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s.
MPEG-1 is the video format that has had some extremely popular spin-offs and sideproducts, most notably MP3 and VideoCD.
MPEG-1's compression method is based on re-using the existing framematerial and using psychological and physical limitations of human senses. MPEG-1 video compression method tries to use previous frame's information in order to reduce the amount of information the current frame requires. Also, the audio encoding uses something that's called psychoacoustics -- basically compression removes the high and low frequencies a normal human ear cannot hear.
Resolutions that video streams can use, are:
352x480 (NTSC, MPEG-2 & MPEG-1)
352x576 (PAL, MPEG-2 & MPEG-1)
352x240 (NTSC, MPEG-2 & MPEG-1)
352x288 (PAL, MPEG-2 & MPEG-1)