The process of encrypting and decrypting the data is called Cryptography. It facilitates the users to store vulnerable data or transmit it through insecure networks so that it is able to read only by the expected recipient.
Data that can be read and understood without any particular measures is known as plain text where as the method of distinguishing plain text for the sake of hiding its stuff is known as encryption.
Encrypted plain text is called as cipher text and the process of returning back the encrypted data to plain text is called as decryption.
A cryptographic algorithm functions in association with a key(can be a number, phrase or word) to encrypt the plaintext and the same plaintext encrypts to various ciphertext with various keys.
Hence, this encrypted data is entirely reliant couple of parameters i.e- the strength of the cryptographic algorithm and the confidentiality of the key.
Symmetric Encryption -conventional cryptography, also called as Conventional encryption. Here, a single key is employed both for encrypting and decrypting.
Below are some examples: DES, MARS by IBM, Triple DES algorithms, RC2,RC4, RC5,RC6.
Asymmetric Encryption - Asymmetric Encryption is Public key cryptography that employes a pair of keys for encrypting the data: a public key, that encrypts the data, and a private key employed for decrypting the data. Public key is displayed to the people when keeping the private key secret. Eg: Digital Signature Algorithm (DSA), RSA, Elgamal
Hashing - Hashing is ONE way encryption, which the scrambled result that cannot be inverted or at least cannot be inverted simply that is used to validate the nobelity of data.
Below are some examples: MD5 algorithm. It is employed to create, Storage of passwords , Digital signatures, Digital Certificates ,Verification of communications.