Elements Side Panel
The Elements side panel lets you try out CSS selectors and lists all matching elements on the page. Selectors can be entered via the Try a selector... field or by right-clicking a selector inside the CSS Panel and choosing Get Matching Elements from the context menu.
Doing so will list all elements, that match the entered selector.
 Context Menu
The context menu for the matching elements is the same as for the HTML elements inside the HTML panel.