What's the difference between a shaved o-ring and silicone o-ring, or silicone recessed???
A shaved o-ring is just that: it's a stock o-ring that's been shaved to sit flush with the recess it rests in. A silicone o-ring is essentially the same thing, albeit with arguably better response. Some of these will already sit flush in the recess, some will need to be shaved to achieve the same result.
Recessed silicone is something done with flowable silicone. This is when you fill a recess with silicone, and then scrape into the recess with a curved object (i.e. a spoon) to remove just a little more silicone than would have been necessary to make it dry flush with the inside wall. The result is silicone that has a concave shape in the middle of the recess it rests in. This is considered by many to be the ideal response setup. Your mileage may vary.