It's a little bit of a challenge to answer, because the quality (and subsequent impact) of these camps can range from cattle call to legit final eval needed to close the deal.
The general process is evals, drills, and personal coaching. Usually for one or two days, one if it's PO, but two if it's for two way players or even just a day for hitting and defense drills/evals, 2nd day for live pitching/batting scrimmage.
In the worst case scenario, you've been targeted at a large showcase eg Showball and you're just a paying customer hoping you'll break through. In the best case scenario, you're a player the school is interested in and they really do want to see more of you and will get more aggressive with you during and after the camp.
My son experienced both. You'll know pretty quickly what kind of camp and/or prospect you are.