WordPress is the most popular content management system (CMS) on the web. Roughly 40% of websites on the internet are built with WordPress. WordPress is an open source software application which means that anyone can host it on their servers as a service for customers and the host does not pay anything for the software. This is why you can host a WordPress website on almost any hosting provider you can find. This does not mean that it’s free for customers and you will generally have to pay a fee to host your WordPress website. https://en-au.wordpress.org/
It is popular because it has a system of plugins and prebuilt features which makes building a website or webshop much easier than developing the code from scratch. It can take weeks of effort, often by a whole team, to build a moderately complex web application with a modern programming language. On the other hand, a small business with typical requirements can get a WordPress website up and running in the space of hours or a few days, depending on the complexity.
What about webshops? As I mentioned before, WordPress has a system of plugins one of which is WooCommerce. https://woocommerce.com/ WooCommerce turns WordPress into a fully featured webshop and it’s the most popular web shop online with around a 1/3 of all web shops being built on WooCommerce. WooCommerce is installed from within WordPress as a plugin and has a slew of different features from digital downloads to dropshipping to traditional inventory based businesses. Many of these plugins will cost you a few hundred dollars a year, so it pays to make sure you know what you’re doing when you buy them.