WordPress stores your website content in a database. It includes your posts, pages, comments, categories, tags, custom fields, users, and other WordPress settings.
You may remember that when you installed WordPress, you were asked to provide a database name, host, username, and password.
WordPress uses the MySQL database management system, and it runs as an application on your web server. This uses some of the server’s resources whenever someone visits your site.
Before a visitor can view a web page on your WordPress website, some scripts run that load the content from your database and create an HTML web page that the user’s browser can display.
When a lot of visitors visit your WordPress website at the same time, there will be a lot of requests to your database and your site will load slower.
For more detailed information and an infographic, see our guide on how WordPress actually works behind the scenes.