The config.bin file is a binary version of the config.cpp file. For more detailed information see Config.cpp.
Sometimes binary form configs are referred to as 'encrypted'. This is misleading, as the encoding used for config.bin is not an encryption, and it was never intended to be, The purpose of the binary form is to provide a representation which can be read by the game engine as fast as possible, avoiding any text parsing.
The encoding of this binary data differs from product to product.
raP File Format - OFP
raP File Format - Elite
raP File Format - ArmA