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.
HTTPS Everywhere
HTTPS Everywhere was inspired by Google's increased use of HTTPS and is designed to force the usage of HTTPS automatically whenever possible. The code, in part, is based on NoScript's HTTP Strict Transport Security implementation, but HTTPS Everywhere is intended to be simpler to use than NoScript's force HTTPS functionality which requires the user to manually add websites to a list. The EFF provides information for users on how to add HTTPS rulesets to HTTPS Everywhere, and information on which websites support HTTPS.