A public key is part of the cryptographic key pair used in cryptocurrency. Unlike a private key, a public key can be shared.
How public keys are used
Public keys help verify that a transaction signature came from the matching private key. In many systems, the wallet address people use to receive funds is derived from the public key.
Public key vs wallet address
A wallet address is usually a shorter, encoded form made for sharing and receiving payments. The public key is a deeper cryptographic value used by the network to verify signatures.
You can share a receiving address, but you should still be careful about privacy. Public blockchain activity can often be traced from address to address.