Difference between universal apps and the rest?

[dnc1916]

I've downloaded a number of apps now and they are organised into 3 different folders in my iTunes:
1. iPhone, iPod Touch and iPad apps (presumably what are called 'universal' apps)
2. iPhone and iPod Touch apps
3. iPad apps

Now I don't have my iPad yet but I assume those in (3) are made specifically for iPad and run full screen high resolution etc. (2) I assume are those apps which are not yet modified for iPad but will still run on the iPad but at a small size in low resolution or they can be doubled up to larger size but by all accounts tend to look grainy cos they are low resolution.

My question is what are those in (1) - the universal apps? Is it an app which displays correctly in small (normal) size on the iPhone and when it is synced to the iPad it also displays correctly in a higher resolution larger size? How are they different from (2) or (3)?

I just want to know before I go spending any more money buying apps in advance!

Thanks

[ct2k7]

A universal binary contains both iPad and iPhone/iPod versions and will display correctly, ie have design profiles for both iPad and iPhone/iPod.

Group 2 and 3 are specific to the device, and for group 2, you'll need to display at 1x or 2x on the iPad.

[dnc1916]

Ok that clears that up. Thanks!