You can use it both to drill 90 degree holes and to drill holes in the depth you want. It also works for joining two woods together, you can see in the video.
In this video, I am making a pocket hole jig. I made a scrap of hard wood. It was a great jig. You should watch this video to learn how to make a kreg jig.
In this DIY video I am making Taper Jig - Jointer Jig for my tablesaw. I used some plywood. It is very useful jig. It is very easy to cut angled and straight with this...