In symmetric encryption the same key is used to encrypt and decrypt a message. in asymmetric encryption different keys are used to encrypt and decrypt. give at least one reason why asymmetric encryption is useful

A useful advantage of Asymmetric encryption over symmetric encryption is that there is no secret channel necessary for the exchange of the public key, unlike in the symmetric encryption which requires a secret channel to send the secret key.  

Another advantage of Asymmetric encryption is that is has increased security. Asymmetric uses two different keys (Public and private) for both encryption and decryption of data while symmetric uses one.

plot immersion i am not fully sure with it though