Describe how public key encryption works.?

What will be an ideal response?

In public key encryption , data is encrypted using two keys: One is a key known only to a user (that is, a private key), and the other is a public key associated with the user. A user's public key can be obtained the old-fashioned way-by asking that user-or it can be  obtained from a third-party source, such as a public key server. Apublic key server is a publicly accessible host (such as a server on the Internet) that freely provides a list of users' public keys, much as a telephone book provides a list of peoples' phone numbers.