What’s the difference between Symmetric and Asymmetric encryption?

To boil down an extremely complicated topic into a few short words, Symmetric encryption uses the same key to encrypt and decrypt, while Asymmetric uses different keys for encryption and decryption. Symmetric is usually much faster, but is difficult to implement most times due to the fact that you would have to transfer the key over an unencrypted channel. Therefore many times an Asymmetric connection will be established first, then send creates the Symmetric connection.