Encryption
In plain terms
Scrambling data so only someone with the right key can read it.
Going deeper
Encryption uses a mathematical algorithm and a key to turn readable plaintext into unreadable ciphertext. Only the matching key reverses it. It protects data in transit (HTTPS) and at rest (disk), so even if someone steals the data, it's gibberish without the key.
Under the hood
Symmetric (AES) is fast for bulk data; asymmetric (RSA/ECC) handles key exchange and signatures. Key management, not the algorithm, is usually the weak point.
Examples
HTTPS/TLS, disk encryption, AES-256, RSA key pairs, end-to-end messaging.
Think of it like...
Like a locked diary: anyone can hold the book, but the words only make sense to whoever has the key.