The code defines a JavaScript function named "toggleNav" which toggles...

The code defines a JavaScript function named "toggleNav" which toggles the presence of a CSS class named "nav-active" on the body element of an HTML document.

When the function is called, it first retrieves a reference to the document body using the "document.body" property. Then, it calls the "classList.toggle()" method on that body element's classList property, passing in the string "nav-active" as an argument.

If the body element already has the "nav-active" class, then calling toggle() removes it. If it doesn't have the class, then toggle() adds it.

So, essentially this function adds or removes the 'nav-active' class from the body element each time it's called, allowing for dynamic changes to be made to the styling of the page.