WordPress is open source content management system software written in PHP that allows users to create and edit websites from a central control panel. It uses a directory and file structure with three main directories - wp-admin for administration, wp-content for custom files like themes and plugins, and wp-includes for core files and application logic. The GNU GPL license guarantees users freedom to use, study, share, and modify the WordPress software. Content on WordPress can include text, images, and is separate from the site structure and design.