Data Compression.

1. What is data compression?
   Data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use.
2. What is a data compression ratio?
   Computer science term used to quantify the reduction in data-representation size produced by a data compression algorithm.
3. Why is data compression an important technique for the online world?
   Because users want faster downloads so minimizing the file size will increase the speed.
4. What is the difference between Lossy and Lossless data compression?
   Lossy image compression is used in digital cameras, to increase storage capacities with minimal degradation of picture quality, Whilst  lossless is in contrast to loss data compression which only allows an approximation of the orginal data to be reconstructed, in exchange for better compression rates. 
5. Which method offers the greatest compression ratio?Lossless data compression.
6. Why is human psychology and perception an important factor in methods of Lossy compression?
   Methods of psychoacoustics are used to remove non-audible (or less audible) components of signal. Compression of human speech is often performed with even more specialized techniques, so that "speech compression" or "voice coding" is sometimes distinguished as a separate discipline from "audio compression". 
   Name Lossy file formats for audio, still image and video format.
   Mp3, JPEG and Mpeg.