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.
Redux Framework is a modular PHP library that allows developers to create customisable settings panels and controls for WordPress projects, providing a consistent user interface for managing options and settings.
WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system.
WPMU DEV Smush is a WordPress plugin that allows you to optimise images without losing quality.