What is the difference? Can someone give a short summary?
2. Which one is called 'laptop'?
I have noted the following:
Laptops> the first foldable, portable computer with battery operation, plentiful connections, drive, from today's perspective quite heavy and thick
Notebook> the further development of laptops, more modern components, lighter, thinner, less power, but still with plenty of connections and a drive
Netbook> stripped-down notebooks, designed for Internet use, cheaper, smaller screens, few connections, no drive
Ultrabook> Notebooks of particularly small and fine design, extremely thin and light, manufacturers have to meet the requirements of Intel in order to be able to call their device "Ultrabook".
If you want to know more about it, you can google it. There are plenty of opinions, because apart from "Ultrabook" there's no one who has sovereignty over the names.