What do the private key and public key in the blockchain mean?

The terms private key and public key are the simplest of all exam questions.

A public key is called a public key, and only what you know is called a private key.

Public key and private key are key pairs (i.e. public key and private key) obtained by algorithm. The public key is the public part of the key pair, while the private key is the non-public part.

Make it clear in one word ~