Bootstrap is a free and open-source CSS framework directed at responsive, mobile-first front-end web development. It contains CSS and JavaScript-based design templates for typography, forms, buttons, navigation, and other interface components.
Font Awesome is a font and icon toolkit based on CSS and Less.
Polyfill is a service which accepts a request for a set of browser features and returns only the polyfills that are needed by the requesting browser.
Popper is a positioning engine, its purpose is to calculate the position of an element to make it possible to position it near a given reference element.
WhatsApp Business is a free to download app available on Android and iPhone using which businesses can connect with their customers.