Apache is a free and open-source cross-platform web server software.
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.
Unix is a family of multitasking, multiuser computer operating systems.