I am familiar with some UI terms but certainly not all. I remember smiling when I figured out what people meant by the term "snackbar" (and have now designed one myself).
However, there is a button which normally has a small-ish triangle to the right. Normally you click the button and a single action happens, however if you specifically click the "small-ish" triangle, you'll get a dropdown list of options. The default one is typically the one you'd have gotten had you just clicked the main part of the button. But the other options are things an advanced user might want to do. Another thing I've seen on the side is a .. but rotated 90 deg.
Screenshot: 
Again, my question is what the normal term is (if there is one). any additional link to a VueJs example would be over the moon.
