Cryptography is the name of a process that allows data to be stored in a coded form. Once this is done it can only be read or processed by select individuals who have the cryptographic key required. This makes it perfect for securing and keeping data private. Cryptography converts information into a form that can only be understood by authorized users. So, nobody else can decode the information and steal or otherwise compromise it.
Modern cryptography is used to make data confidential and also render it immune to tampering, either while it is being transmitted from place to place or while it is being stored. It also prevents the creator of the data from being able to deny that they sent it. Cryptography provides concrete proof of attribution.
This is why information security relies on cryptography. There are many algorithms available to the cryptographer, including SKC or Secret Key Cryptography, PKC or Public Key Cryptography and Hash Functions.