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.
Public key infrastructure
PKIs of one type or another, and from any of several vendors, have many uses, including providing public keys and bindings to user identities which are used for:
Some argue that purchasing certificates for securing websites by SSL and securing software by code signing is a costly venture for small businesses. However, the emergence of free alternatives such as Let's Encrypt, has changed this. Presently Symantec holds a major share in PKI certificate market which sold one third of all certificates issued globally in 2013. HTTP/2, the latest version of HTTP protocol allows unsecured connections in theory, in practice major browser companies have made it clear that they would support this state-of-art protocol only over a PKI secured TLS connection. Web browser implementation of HTTP/2 including Edge from Microsoft, Chrome from Google, Firefox from Mozilla, and Opera supports HTTP/2 only over TLS by using ALPN extension of TLS protocol. This would mean that to get the speed benefits of HTTP/2, website owners would be forced to purchase SSL certificates controlled by corporations such as Symantec.