What is the drop down arrow called?
It's called a caret. It looks kind of like a triangle or a pyramid, and it kind of functions like an arrow.
How do I add a drop down arrow in HTML?
Use any element to open the dropdown menu, e.g. a <button>, <a> or <p> element. Use a container element (like <div>) to create the dropdown menu and add the dropdown links inside it. Wrap a <div> element around the button and the <div> to position the dropdown menu correctly with CSS.