[Help] What is an hash code?

Hello,
what can i do with a hash code?
im asking because of this:
http://www.mpgh.net/forum/33-visual-...ns-vb-net.html
Please tell me what is it/

In cryptography, MD5 (Message-Digest algorithm 5) is a widely used cryptographic hash function with a 128-bit hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. However, it has been shown that MD5 is not collision resistant; as such, MD5 is not suitable for applications like SSL certificates or digital signatures that rely on this property. An MD5 hash is typically expressed as a 32-digit hexadecimal number.



EVERY file has a different md5 hash even if you just change one char in a textfile, the md5 hash will be different.

This is useful for updaters for instance.

It is alphabetic-numeric.