WordPress is a content management system often just referred to as an CMS. There are many other CMS used to develop websites, both web based and as internal intranets.
We started with Joomla, I think. It has been so long. But we had stints with Mambo, Concrete5 and I did a site on special request using Drupal. I also did a site using the e-commerce platform called Magento.
For a few years now I settled on using WordPress for business sites and add WooCommerce on top for e-commerce websites. I started with WordPress by accident. I outsourced lots of the Joomla work but had a client insisting on a WordPress blogging site. No one in my immediate circle wanted to work in WordPress. I had to roll up my sleeves and get it done. Within a few days I handed over the site to the client who was pleasantly very happy with it. She was a Swedish journalist, Anika.
This is how I stayed in the WordPress ecosystem and have subsequently invested in it. I bought many plugins, also called software, to enhance WordPress. I continue to learn and improve my skills to deliver the best possible site that a clients budget can afford.