WordPress is an open-source content management system (CMS).
Open-source means WordPress can be freely downloaded and modified.
Content Management System means WordPress is a system to create and manage your webpage content.
WordPress separates webpage content from the website design.
What this means is WordPress allows you to edit the webpage content, without necessarily affecting the overall website design.
This allows for a universal website design, which surrounds the webpage content like text, images and videos.
The website design is controlled by a template, called a Theme.
As a CMS, WordPress websites’ functionality can be extended using Plugins. Plugins might add e-commerce functionality for instance.
So, overall, WordPress is a flexible way to build a website where you take care of the text, images and videos, and professional website designers take care of the website design by producing WordPress themes, which you can use, and website developers extend the functionality of your website using WordPress plugins.