WordPress is an online, open source website creation tool written in PHP. But in non-geek speak, it's probably the easiest and most powerful blogging and website content management system (or CMS) in existence today.
Magento is an ecommerce platform built on open source technology which provides online merchants with a flexible shopping cart system, as well as control over the look, content and functionality of their online store.
AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and lets you extend HTML's syntax to express your application's components clearly and succinctly.
OpenCart is an online store management system. It is PHP-based, using a MySQL database and HTML components. Support is provided for numerous languages and currencies, and it is freely available.
Drupal is free, open source software that can be used by individuals or groups of users -- even those lacking technical skills -- to easily create and manage many types of Web sites.
PHP is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.