Data compression is the compacting of information by decreasing the number of bits that are stored or transmitted. Consequently, the compressed data will need less disk space than the initial one, so additional content could be stored using identical amount of space. You'll find various compression algorithms that function in different ways and with many of them just the redundant bits are removed, which means that once the info is uncompressed, there's no decrease in quality. Others remove unneeded bits, but uncompressing the data subsequently will result in reduced quality compared to the original. Compressing and uncompressing content takes a large amount of system resources, in particular CPU processing time, therefore every web hosting platform which employs compression in real time needs to have ample power to support that attribute. An example how info can be compressed is to replace a binary code such as 111111 with 6x1 i.e. "remembering" what number of consecutive 1s or 0s there should be instead of keeping the whole code.