Bootstrap is a free, open-source front-end library for creating responsive, mobile-first websites. It includes HTML and CSS-based design templates for typography, forms, buttons, navigation and other interface components, as well as optional JavaScript extensions.
Flatsome is a modern, responsive WooCommerce theme that helps you create a beautiful online store. It features a drag & drop page builder, live theme customizer, and tons of customization options to make your store stand out.