ENCRYPTION

In cryptography, encryption is the process of transforming information (referred to as plaintext) using an algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information (in cryptography, referred to as cipher text). In many contexts, the word encryption also implicitly refers to the reverse process, decryption (e.g. “software for encryption” can typically also perform decryption), to make the encrypted information readable again (i.e. to make it unencrypted).
Encryption is also used to protect data in transit, for example data being transferred via networks (e.g. the Internet, e-commerce), mobile telephones, wireless microphones, wireless intercom systems, Bluetooth devices and bank automatic teller machines. There have also been numerous reports of data in transit being intercepted in recent years [2]. Encrypting data in transit also helps to secure it as it is often difficult to physically secure all access to networks. Encryption, by itself, can protect the confidentiality of messages, but other techniques are still needed to protect the integrity and authenticity of a message; for example, verification of a message authentication code (MAC) or a digital signature. Standards and cryptographic software and hardware to perform encryption are widely available, but successfully using encryption to ensure security may be a challenging problem. A single slip-up in system design or execution can allow successful attacks. Sometimes an adversary can obtain unencrypted information without directly undoing the encryption. See, e.g., traffic analysis, TEMPEST, or Trojan horse.
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Lets c the following scenario.:
There is a software which encrypts information in the following way .It adds 3 to each alphabet before sending it and at the receiving end there is a software which subtracts 3 and again decrypts it for the receiver.
Suppose A is the sender n B is the receiver .
A sends the messege “ABC”.. after passing through encryptor it becomes ”DEF”. if the data is now leaked then the person receiving the leaked data will get “DEF” instead of “ABC”..now we no that 3 has been added to each alphabet the person receiving it doesn’t no what has been added so it is tough to get the original messege.Now when the data reaches the receiver end the decrypting software subtracts 3 and the original text is revived

THIS WAS A VERY SIMPLE EXAMPLE .REAL WORLD ENCRYPTION PROCESS ARE MUCH MORE COMPLICATED AND COMPLEX THUS THE SKILL REQUIRED BY HACKERS IN DEFEATING THEM IS ALSO VERY HIGH
Some of the encryption algoritms

RSA
DES/3DES
BLOWFISH
IDEA
SEAL
RC4

IF U WANT TO NO MORE ABOUT JUST GOOGLE THEM