In cryptography, encryption is the process of encoding messages (or information) in such a way that eavesdroppers or hackers cannot read it, but that authorized parties can.  In an encryption scheme, the message or information (referred to as plaintext) is encrypted using an encryption algorithm, turning it into an unreadable ciphertext. This is usually done with the use of an encryption key, which specifies how the message is to be encoded.

There are two basic types of encryption schemes : private-key encryption and public-key encryption. In private-key schemes, the encryption and decryption keys are the same. Thus communicating parties must agree on a secret key before they wish to communicate. By contrast, in public-key schemes, the encryption key is public: that is, anyone (friend or foe) has access to the encryption key, and can encrypt messages. However only the receiving party has access to the decryption key and thus is the only one capable of reading the encrypted messages. Public-key encryption is a relatively recent invention: historically, all encryption schemes have been private-key schemes.  (Source: Wikipedia)

The video below demonstrates how the tech companies and banks use the encryption technique to encode their digital data for security reasons. Banks, Facebook, Twitter and Google use epic numbers – based on prime factors – to keep our Internet secrets. This is RSA public-key encryption. See the video below for the detail explanation: