What is the use of LOGGING_FACILITY compared to NSLog in iOS?

I am working on creating key pairs for RSA Algorithm. I was looking into Apple's sample project on Crypto, http://ift.tt/1gvqmQL

See the below code

sanityCheck = SecKeyGeneratePair((__bridge CFDictionaryRef)keyPairAttr, &publicKey, &privateKey);

LOGGING_FACILITY( sanityCheck == noErr && publicKey != NULL &&     privateKey != NULL, @"Something really bad went wrong with generating the key pair." );

I found LOGGING_FACILITY is used. I understand it is used for logging purposes. Can anyone elaborate what is the difference between LOGGING_FACILITY and NSLog? Also show pointers to Apple's documentation explaining on the usage of LOGGING_FACILITY