I was passed over in 2016 and 17, so the data is a bit dated. However, I wouldn't be surprised if the process hasn't changed at all. Expect continuation to be offered if you're in a critical career field. It's an individualized letter you get and are required to sign, so read everything carefully. If it's confusing, grab a personalist to de-code it before you sign.
If passed over, you're supposed to get a sit-down with your commander to cover all the details and what to expect next. Grill him on details in that interview and get your ranking as he pushed you out of the squadron, as well as your ranking in the wing. That's less about fixing something and more about accountability. Any commander worth his salt should already be digging in to see exactly why you didn't make it.
After all that, you get a one-on-one phone counselling with a AFPC civilian who's whole existence is promotions and passed over stats. That is about looking at the numbers for your entire promotion group and examining some of your peer group packages that were right on the cut-off line to see what they had vs what you had.
That's what's supposed to happen. In my case, I got a phone call from my supervising O-6 who was two countries away saying 'sorry, you didn't make it, good luck'...and I had to figure all this out on my own, so beware: mileage may vary. I will simply highlight that it's your boss's job to dig all this up and explain it, but there are also a lot of useless bosses out there.
As your profile says you're at RND, you should be able to go direct to the source for councelling...or simply to kick those AFPC clowns in the shins...