By the look of the space between them, it looks like three separate windows.

How do you frame three separate windows?

This looks to be three separate windows

so, I guess that means if I want a bay type window over my kitchen sink, it would be best to buy 3 separate sized windows since some bay windows are limited to size?

The bay window on the picture is made up of 3 separate windows with a wall partitions between each.
Bay windows we install are made of 3 windows that are joined/connected with matching colour corner post fixed to suit angle of the bay (90 degree for square). From the inside, you won't see it. From the outside, the thickness of the post matches the thickness of the profile window is made of + 4mm approx. Finished effect is as one window with a separate glazing. You can see sample in the gallery of our website www.avantewindows.ie

This is a bay window with a large wood panel on either side of the central fixed window (that contains a really neat grid pattern). The narrow windows on the sides open to allow ventilation. So yes, there are 3 separate windows used in combination to appear as a single unit.

I agree with everything above. I would point out that there appears to be a crank at the lower portion of the two side windows. That being the case, the two side windows are likely to be casement or awning windows. (With an SDL about half way up to create a single hung look). Clever, very clever!

Jeff in Houston