jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
OpenResty is a web platform based on nginx which can run Lua scripts using its LuaJIT engine.
Stripe offers online payment processing for internet businesses as well as fraud prevention, invoicing and subscription management.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.