How does an md5 hash work specifically?

In cryptography, MD5 (Message-Digest algorithm 5) is a widely used, partially insecure cryptographic hash function with a 128-bit hash value. As an internet standard (RFC 1321), MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. An MD5 hash is typically expressed 32-character string of hexadecimal numbers.

The MD5 hash also known as checksum for a file is a 128-bit value, something like a fingerprint of the file. There is a very small possibility of getting two identical hashes of two different files. This feature can be useful both for comparing the files and their integrity control. Let us imagine a situation that will help to understand how the MD5 hash works. Alice and Bob have two similar huge files. How do we know that they are different without sending them to each other? We simply have to calculate the MD5 hashes of these files and compare them.

The MD5 hash is used in many websites.