Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Publisher Tag (GPT) is an ad tagging library for Google Ad Manager which is used to dynamically build ad requests.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Open Graph is a protocol that is used to integrate any web page into the social graph.
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.