Imagine you and your friend committed to a secret language that only the two of you know. For instance, you exchange "apple" for "hello" and "banana" for "goodbye". This way, if you drop an "apple" or a "banana" in a conversation, only you two know the real message. That's basically how cryptography works, but with a far more complex scale and encoding systems!

The difficulty to decode the information depends on the key, which is a piece of information that determines the output of a cryptographic algorithm. Think of it as a decoder ring from your favorite childhood spy movie – without the correct one, you wouldn't decipher the coded messages.

There are two main types of cryptography: symmetric and asymmetric. Symmetric is like sharing a secret password with your friend – you both know it and use it to decipher the code. On the other hand, asymmetric consists of two related keys, a 'public key' that you give out freely and a 'private key' that you keep secret. Anyone can use your public key to encode a message, but only the private key – that you keep – can decode it.

In a digital age where cyberangels and cyberdemons exist, cryptography keeps your information away from the prying eyes of the latter. It is essential for computer passwords, online transactions, and protecting the integrity of websites and digital data.

In summary, cryptography involves encoding messages to maintain privacy. It uses complex algorithms and keys to protect communication and secure information in the vast arena of the internet, working towards a singular goal – to protect data, ensure confidentiality, and uphold user trust online.