Beginner
Cryptography
Encryption
Scrambling data with a key so only someone holding the matching key can read it.
In simple terms
Encryption turns readable plaintext into unreadable ciphertext. With the right key it comes back; without it, you get noise.
Analogy
A locked box: anyone can carry it around, but only the key holder can open it.
Going deeper
Modern schemes are almost always authenticated (AEAD): AES-GCM or ChaCha20-Poly1305 provide confidentiality and integrity together, so tampered ciphertext fails loudly instead of decrypting to garbage. Nonce uniqueness is part of the contract.
Common mistake
Base64 and simple obfuscation are not encryption — without a key managed separately from the data, there is no confidentiality.