Let’s illustrate with a really cool example…

According to the good folks of Wikipedia…

Time-lapse photography is a cinematography technique whereby the frequency at which film frames are captured (the frame rate) is much lower than that which will be used to play the sequence back. When replayed at normal speed, time appears to be moving faster and thus lapsing. For example, an image of a scene may be captured once every second, and then played back at 30 frames per second; the result would be an apparent increase of speed by 30 times. 

Processes that would normally appear subtle to the human eye, such as the motion of the sun and stars in the sky, become very pronounced.  Another example: Watching a 125 foot tall dam on the White Salmon River be removed in one minute. (ok, that last part’s not from Wikipedia)