I'm no expert, but it looks like a round-cut bezel set diamond. It's also extremely gorgeous. From one engaged woman to another, congrats!
Yes they lead to marriage which leads to happiness which turns to hate which leads to divorce...<br />
Three C's: Cut, Carats, & Clarity. Obviously round cut, Clarity cannot be determined from a photo. VS1 and VS2 are not as bad as you might imagine. They indicate minor inclusions visible under 10X magnification and are less expensive than clearer stones. The final is Carats - unless you have tiny hands, that looks like at least a full carat - a very respectable size, unless your a Diva and want something costing well into 5 figures.
Rule of thumb is the ring should cost 3 or 4 times what he makes in a month. Ive heard 3 times and Ive heard 4 times.
a reputable appraiser can give you all that information and more, but he would need to examine the ring, not a picture, to do any more than put names to the cut and the setting.
It's round. That link tells more about round cuts.<br />
The setting is a bezel setting.