There are two kinds of components that you can add to your app -- Visible components that appear on your screen and Invisible or sometimes referred to as API components that work across screens in the background.
Visible components have common sets of properties usually sizing, styling & text styling, spacing, positioning. You may often have multiple visible components on a single screen and sometimes dozens if not hundreds in a single app.
Invisible components often require some set-up and usually are limited to one type of invisible component per app (since you do not need to add them across screens