Public key crypto lets us share secret information with other devices on the Internet, without letting eavesdroppers listen in.
Video notes: cys.me/vid/c03.
Video #4 describes SSL/TLS (Transport Layer Security) vimeo.com/197456690
The previous video explains the eavesdropping problem vimeo.com/189541035
See the entire Cryptosmith series in its album vimeo.com/album/4229550
The video series Grade School Crypto provides additional background information vimeo.com/189517140