In the following picture, I have mocked up a CSS active menu styling I would like to find examples of, and hopefully replicate.

You will notice there is a triangle highlighting the active menu, and it can appear bold too.
Question 1. What is this “active menu triangle style” actually called? So I can find CSS examples of it.
Question 2. Where can I find examples of this?
All done through css classes like so:
html
css
Tweak the background-position until it fits snuggly with the border.