Data Compression reduces the amount of data that needs to be retained in order to ensure that the original information content of the data is maintained. When moving data across a network it can reduce the size of the data set that needs to be transmitted. This can be done in a lossless or in a lossy way. Lossless compression removes data from the data set in such a way that it can be added again when the data arrives at its destination. For example, removing characters that repeat and instead including a value saying how many of these characters there should be. Lossy compression removes data that is not required for the receiver to use the data. A typical example is reducing the colour depth information in images. Often this can be reduced significantly without noticeable degradation to the transmitted image.