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.
Lightbox is small javascript library used to overlay images on top of the current page.
Modernizr is a JavaScript library that detects the features available in a user's browser.
PHP is a general-purpose scripting language used for web development.
UIKit is the framework used for developing iOS applications.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.