Cryptography Vs. Encryption
Many people use the terms encryption or cryptography interchangeably. However, they are different. Cryptography is the science of secret communication, while encryption refers to one component of that science. Get the basic definitions here.
What is Cryptography?
In simple terms, cryptography is the science concerned with the study of secret communication.
If you look at the origin of the root words of cryptography (crypto and graphy), you will see that "crypto" stands for "hidden, secret", and "graphy" denotes "a process or form of drawing, writing, representing, recording, describing, etc., or an art or science concerned with such a process." So you can see that cryptography is indeed the science concerned with secret communication.
If you check Google to see what the term "cryptography" means (i.e. "define: cryptography"), you will see a long list. And if you checkdictionary.com you will at least see three variation of its definition:
The science or study of the techniques of secret writing, esp. code and cipher systems, methods, and the like.Compare cryptanalysis (def. 2).
The procedures, processes, methods, etc., of making and using secret writing, as codes or ciphers.
Anything written in a secret code, cipher, or the like.
With the advent of digital technology, the need for secure communication has greatly expanded. This makes cryptography even more importnat than ever before.
What is Encryption?
If you breakdown the the base word--"encrypt"--into its root, you will see "en" and "crypt". The "en" part means "to make", and the "crypt" part (a variation of "crypto") means hidden or secret. Since "encrypt" is a verb, the base term then means "to make hidden or secret".
Thus "encryption" basically is some process or algorithm (known as a cipher) to make information hidden or secret. And to make that process useful, you need some code (or key) to make information accessible.
About Ciphers
There are many types of ciphers developed over time.
In the days of written communication, most common ciphers involved some form or substitution or transposition of alphabetical letters. Substitution means to substitute one character for another while transposition is some form of repositioning characters within the message (which literally scrambles the information).
In the digital age, ciphers changed and are generally based on two types of algorithms--one using the same key to encrypt and decrypt, and one using different keys to encrypt and decrypt (also known as symmetric and asymmetric key algorithms, respectively). The one that uses symmetric keys falls under private-key cryptography, while asymmetric key algorithms falls under public-key cryptography. DES (Data Encryption Standard) and AES (Advanced Encryption Standard) are two well known ciphers based on symmetric key algorithms, while RSA (Rivest, Shamir and Adleman) is a well known cipher based on asymmetric key algorithms.
Conclusion
Clearly and simply the term cryptography is the study or science of secret communication, while encryption is simply a component of that science. Encryption is the process of hiding information, through the use of ciphers, from everybody except for the one who has the key. Encryption is a direct applicaton of cryptography, and is something that websites use every day to protect information.
In today's digital world, there are two major types of ciphers--one based on symmetric and one based on asymmetric key algorithms.