HTTPS
Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP) for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is encrypted using Transport Layer Security (TLS), or, formerly, its predecessor, Secure Sockets Layer (SSL). The protocol is therefore also often referred to as HTTP over TLS, or HTTP over SSL.
HTTP Public Key Pinning
HTTP Public Key Pinning (HPKP) is an Internet security mechanism delivered via an HTTP header which allows HTTPS websites to resist impersonation by attackers using mis-issued or otherwise fraudulent digital certificates. It does this by delivering a set of public keys to the client (e.g. web browser), which should be the only ones trusted for future connections to the same domain name.