Amazon Pay is an online payments processing service that is owned by Amazon. It lets you use the payment methods associated with your Amazon account to make payments for goods and services.
Fly is a platform for running full stack apps and databases.
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.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.