I know those as:
ball terminals (references: 1, 2),
teardrops or teardrop terminals (reference),
The one on the top right of a binocular g is usually called ear, irrespective of its shape (references: 1, 2). You could describe your example g as having a teardrop ear, I suppose.
Note that terminal is usually used in a much wider sense, including several kinds of ends of strokes, e.g., the bottom right end of the letter c in your example does not feature a circular structure, but it would usually still be referred to as a terminal. By contrast, the ear of a binocular g is not a terminal.
is there a typographical significance to them, other than just stylistic?
Well, first of all, using ball terminals very likely originate from calligraphic artifacts and using them in a typeface is a stylistic choice.
However, they do have effects like balancing the black area of the glyph, in particular when there is a strong contrast of stroke widths.
In a related manner, they also avoid the impression that letters will topple or are tilted (mostly relevant at large sizes).
This is easy to see with a binocular g which usually is off balance without its ear, for example:
Also, ball terminals can emphasise distinguishing features of different characters, thus aiding readability.
For example, in the following, the letters v and y from the same typeface are superimposed:
As you can see, the ball terminal makes up most of the red and green area (the difference).
If it wasn’t there, readers may more easily mistake a y for a v.
So, you cannot just remove ball terminals from a typeface without compensating for it, e.g., by changing the stroke widths.