AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
Endurance Page Cache adds basic file-based caching to WordPress.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.