Public Key

A public key is the shareable half of the cryptographic key pair that controls crypto funds; the private key is the secret half. The private key is generated first, and the public key is derived from it mathematically in a way that cannot be reversed, so publishing it does not expose the secret. Wallet addresses are in turn derived from public keys, which is why an address can be shared freely to receive funds. When you send a transaction, your wallet signs it with the private key, and any node can use the public key to check that the signature is genuine without ever learning the key that produced it. Losing or leaking the private key, however, means losing control of the funds.