Symmetric vs Asymmetric Encryption
Symmetric encryption uses one shared key to lock and unlock data; asymmetric encryption uses a linked pair — one public, one private.
In depth
Symmetric is like a house key: fast, but you must somehow hand a copy to the other person securely. Asymmetric solves that handoff — anyone can lock a message with your public key, and only your private key can open it. Cryptocurrencies rely on asymmetric key pairs for ownership and signatures.
Why it matters
It explains why you can publish your address to the world without exposing your funds.