WordPress is a free, open-source Content Management System (CMS) that allows you to build and manage a website without having to learn HTML, CSS, Javascript, PHP or any web scripting language.
WordPress is PHP script that connects to a MySQL database to store and retrieve your website content.
WordPress is installed via your hosting control panel, such as cPanel or a proprietary managed hosting control panel offered by many hosting providers.
The installable components of WordPress are Themes and Plugins. Themes provide the visual appearance, layout, and design of your website. Plugins add custom features such as contact forms, online stores, SEO tools, etc..