RSA is a type of cryptographic technique to enable communication between two parties over an unsecure medium. It was inspired by the work of diffie-hellman in cryptography

A public key is shared between the sender and receiver. The original message is encrypted using the public key and transmitted over to the receiver. The receiver can only decrypt the original message, if they have the private key that is not shared over with anybody.

 References:

1. RSA Algorithm.