MD5 is an algorithm (command line message digest utility) that was created in 1991 by Professor Ronald Rivest. Its main function is to create digital signatures.
It was intended for use with 32 bit machines and is considered to be much safer than MD4, which has been cracked. MD5 is essentially a one-way hash function. This means that is takes a transmitted message and encodes it as a string of fixed digits.
Another term for this process is a message digest.
If one is using a one-way hash function, a person can compare a message digest against the same message digest that has been decrypted using what is called a public key.
This action is performed in order to check and verify that that the message has not been tampered with.
This type of comparison is generally referred to as a ‘hashcheck.’