Freeze-drying is a method of dehydration. If you are buying dehydrated goods there is a good chance that some of them, e.g. instant coffee, will have been done this way.

I have not heard of anyone freeze-drying at home, though if you want to see the effect in action just leave an unwrapped piece of food [maybe a bread bun] in the freezer and observe how it becomes desiccated.