How does WordPress save website changes?

I have been wandering on how WordPress and other CMS platforms save changes to a users website.

They have a lot of Data stored in SQL, is this how they save changes? When a user makes an edit to text or adds in a form how does PhP bring the changes into effect when people visit the website?

The only way I can think of it being done is each part of the website is saved into a Database and PhP pulls the information from the Database to echo it out on the site.

So there would be a table for the homepage, the about page, contact page etc. Image locations and names are saved into the DB and is echoed into the img src to be displayed. Each item such as Blog posts are saved into their own tables and a loop echos each post on the page.

Is this the way they go about it? This seems a little messy but I can't think of any other way they can do it.

This is a simple thought into a complex system that WordPress has built but I am just very curious on how they went about it.

Thank guys