What does the display: none; style do?

The style display: none; effectively removes an element from the document’s layout, making it completely invisible on the page. When this style is applied, the element does not take up any space in the layout, which means that the layout of surrounding elements can adjust as if the hidden element doesn't exist. This is particularly useful when you want to toggle the visibility of elements dynamically using JavaScript or CSS, as it can effectively "delete" the element from visual consideration without actually removing it from the HTML structure.

In contrast, making an element invisible while still occupying space (which describes the second choice) would be done using visibility: hidden;, where the element remains in the flow of the document but is not visible. Shrinking an element to zero size could refer to changing its height or width properties, but display: none; does much more by not contributing visually or spatially. Meanwhile, altering the opacity of an element pertains to making it transparent while still fully occupying space and being functional in the layout.