Websites that have a shopping cart or checkout page, either using a known ecommerce platform or a custom solution.
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.
Shopware is an enterprise-level ecommerce platform.
A modest JavaScript framework for the HTML you already have.