Browser DevTools are tools built into browsers that help people inspect and test a website. They are like a workshop window into a page: you can look at its layout, see messages, and check how it behaves.
If a button appears in the wrong place, the Elements panel can help you inspect the page structure and styles. The Console can show errors that may explain why an interaction is not working.
Changes made inside DevTools are usually temporary experiments, not edits to the website's saved files. To keep a fix, make it in the project files and test the page again.