What are symmetric and asymmetric encryption, and how is each used?

"Encryption is the process of changing the format of a digital message to protect it from being read by an unauthorized user. Symmetric encryption encrypts the data using a key and decrypting the message using the same key. This is easy to implement and creates little additional overhead but is easy to penetrate. It also requires a safe method to transfer the encryption key from the sender to the receiver. Asymmetric encryption is based on public and private key encryption techniques. It employs different keys to encrypt and decrypt the message. While it is more secure than symmetric encryption, it has more overhead and therefore is slower."