Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
Polyfill is a service which accepts a request for a set of browser features and returns only the polyfills that are needed by the requesting browser.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.