What is ZLib?
ZLib is an open source lossless compression library. It supports steaming decompression, unlike LZO. It's licensed under the [ZLib license].
Libraries like ZLib can help speed up load times for games. If data is compressed then there is less data that needs to be transfered from the hard drive, CD-ROM or DVD-ROM, or network, hence speeding things up.
There's a lot more to the ZLib compression library than just what was mentioned here. If you want more information, here are some good places to find it: