An iPhone. The iPad and the iPod can't make regular phone calls.
internet
no, you can't, but you CAN put ipod touch/iphone apps on your ipad
iPhone/iPod Touch/iPad iPhone: 1G, 2G, 3G, 3GS, 4 iPod Touch: 1G, 2G, 3G iPad
Yes. The home button on the iPhone (and the iPad) is bigger than the iPod touch's (and the iPad Mini's)
Its a hack for your ipad ipod or iphone
Macbooks iPod iPhone iPad
Macbook, iPhone, iPad, iPod
Probably iPod touch, iPhone, iPod nano, and iPad.
ipod shuffle
Many apps will work on the iPhone, iPad and iPod Touch. Some are written just for the iPad while others only work on the iPhone and iPod Touch. Under the title in the App Store it will specify which devices the app will work on.
No. iPod Touch, the latest model of the iPod series, was produced shortly after the iPhone. iPad came third.