What is framerate
The frame-rate says how many images of a movie are displayed every second a movie is played.
The higher frame rate a movie has the smoother objects move in the movie.
Compare a movie with low framerate with a movie with higher framerate. The movie with high frame has more frames for the same number of seconds film. The movie with higher framerate will also be stored in a larger file.
You measure frame rate in frames per seconds (fps).
Frame rate in game is the same thing. The only difference between movie frames and game frames are that movie frames are created as you play for a movie they are just recreated from a file.
A constant frame rate is desired for smooth playback. Depending on the compression used in the video file it can put a heavy load on your computer. If the computer is not able to replay the movie at the frame rate it was encoded for it will either stutter and slowdown or drop frames will be dropped.
If you go watch a movie at the cinema you will see it at 24 fps.
If you live in Europe or Asia you watch your TV programs at 50 frames per second in a standard called PAL (Europe) or Secam (Asia). TV is broadcast in something called interlaced mode. Every second frame the odd lines are updated and every other update the even scan lines are updated. The actual refresh is so quick that your brain will compensate and you will see it as normal. The actual refresh rate of a TV is only 25 fps, close to the cinema. The interlaced pictures is mostly visible when the camera pans. It can also be quite visible on videos with slow refresh rate on your computer.
In the USA the TV format is called NTSC and is updated 60 times per seconds and is also interlaced. New images are displayed on screen 30 times per second.
High Definition TVs, HDTV, usually has a refresh rate of 60 frames per second or more and does not use interlaced. When the TV is not interlaced its called progressive, the screen is updated 60 times per second. LCD computer screens also typically use non interlaced refresh.
New 3D TVs need to have even higher frame rate since the percieved framerate in effect is split between the left and right eye. To view 3D at 50 frames per second the 3DTV needs to refersh its display at 100 frames per second. When viewing 3D with low framerate you will experience something called ghosting, shadows of the frame rendered for the other eye. The ghosting effect will go away with higher framerates. When we talk about the higher framerate of the 3DTV we typically only talk about the update of the display ie the same video frame is output several times to the display.
Summary
Frame rate is one of the factors affecting movie file size and quality. The update can be interlaced or non interlaced, progressive.
Links
Learn more about video framerate at wikipedia
