What happens to an element when its visibility is set to hidden?

Setting an element's visibility to hidden means that the element will still be rendered in the HTML document, but it will not be visible on the page. This means that the element is still part of the DOM (Document Object Model) and maintains its position in the document flow, which allows for other elements to be positioned around it correctly.

This behavior is crucial in scenarios where you might want to temporarily hide an element without affecting the layout. For example, if you have a dropdown menu that should appear when a button is clicked, setting the dropdown menu's visibility to hidden allows you to toggle it without disrupting the surrounding content's layout.

The other options describe different behaviors: removing an element entirely from the layout would imply that it's no longer part of the flow (which happens when using display: none), while making an element transparent does not prevent it from being visible; it merely changes its opacity without affecting its layout.