WordPress is a Content Management System (CMS), it is the most popular and most used Content Management System. WordPress has the ability to allow you to make a recent-blog into a famous business-company, or a famous website. WordPress has more themes, more downloads, more plug-ins, and is more free with the community’s support.
There are other Content Management Systems more complex/as complex than/as WordPress.
WordPress is free with guidance, support and it is appropriate for those of new experiences in creating websites and beginners, intermediate individuals, and experts are capable to edit their website in an efficient way.
There were other websites “possibly powered by WordPress”, not powered by WordPress, or is powered by WordPress stating/informing that WordPress is the perfect Content Management System for both progressing and expert-like individuals.
Like how the other websites informs/states, WordPress is free with a little need of payment when you want premium themes, change your domain, etc.
There are other Content Management Systems like Joomla, Drupal, and others. You can access to them, and/or you can transfer your website from Joomla, Drupal, or another Content Management System to WordPress while your posts, pages, and others are hypothetically/authentically safe.
Even small and big companies are powered by WordPress.