Encryption is the balance of encoding data so that malicious investigators cannot read and understand it, yet desirable recipients can. Long gone are the days of Ceasar ciphers and jump codes on paper, however - now most encrypting is done electronically via an encryption algorithm. The result of information run through such an algorithm is known as ciphertext.
The most common method of encryption is done using an encryption key which is needed to decode the ciphertext. This schema can be further divided into public-key encryption and symmetric-key encryption. The former releases the key publicly, allowing anyone to use it to encrypt data, but requires a second, private key to decrypt the data, while the latter uses the same key which must therefore be agreed upon in advance by both parties and kept secret. It is also for this reason sometimes known as private-key encryption.
Encryption has become more important and everyday as computer use increases. Now everything from multinational companies' banking information to your mother's private Facebook messages is kept private via a variety of methods of encryption. Data is increasingly likely to be intercepted in transit through networks, where security is often weakest because of the increased number of machines linked in and therefore the increased number of entry points into the system. Therefore sophisticated encrypting is used to preserve the confidentiality of data in transit. The data's integrity and authenticity however, requires more than just encryption.