Laptop, netbook, ultra book ???

[zapionics<alt>]

I've noticed that there are quite a few different types of portable computer being discussed in the literature, but when I go hunting for exact definitions they're hard to find.

For example I frequently read the terms laptop, netbook, notepad, ultralight, desktop replacement, Rugged, ultra-portable, ultra-mobile, handheld and so on, with many terms often used interchangeably in the the same discussion.

Now I think I'm clear about what a tablet is, probably because it lacks a keyboard and mouse so s very distinct from a laptop. Equally I feel that I am clear about what a laptop is because they've been around for ages.

But all these other terms just seem to be market-speak for the same thing and kinda blend together in my mind.

I mean to me a netbook is just a small laptop...

Is anyone able to say if my perception is wrong, that these devices are all distinct classes in their own right and should be understood as such, or are they all just buzzwords for the laptop? ( Essentially extensions to the class of "portable computer".)

[CrowdAds]

[PeterT]

These are just marketing terms. Here's my understanding of each:
laptop - generic term for any PC that is potable and has a keyboard and mouse (trackpad)
netbook - a small (<=12 in. screen) and low powered laptop with long battery life, suitable for surfing the net, but not much else
notepad - I'm not sure what this is; but maybe it's a tablet
ultralight - a laptop that weighs less than ???
desktop replacement - a laptop that is powerful enough to do everything (3D gaming, video transcoding, etc.) that a traditional desktop can do
Rugged - Panasonic Toughbook
ultra-portable - a laptop that is smaller than ??? and lighter than ???
ultra-mobile - see ultra-portable
handheld - phone? tricorder?

My Asus Eee PC 1215B straddles the following 'categories': laptop, netbook, ultralight, ultra-portable, ultra-mobile, and probably a few others that have or have not yet been coined.