What are the differences between the displays on different iPad models? What is the viewing angle of the iPad? Is the screen visible from the sides or does it have to be held immediately in front of one person?

All iPad models have IPS LED-backlit displays with a viewable angle of 178 degrees horizontally and vertically, which makes it quite possible for more than one person to view the screen simultaneously.

However, the physical size, resolution, and pixel density of the iPad displays vary accordingly:

If you are not sure which iPad you have, see EveryiPad.com's iPad Identification section.

Do all the iPad models have a camera? What are the differences between the cameras on each iPad?

The original iPad models -- the iPad (Wi-Fi) and iPad (Wi-Fi/3G/A-GPS) -- do not have any kind of camera -- still, video, or webcam, and as a result do not support video conferencing.

All subsequently released iPad models have dual video cameras and shoot video and still photographs as well as support video conferencing via applications like Apple's own FaceTime, Skype, and other apps.

The capability of each iPad camera is best visualized as a chart:

If you are not sure which iPad you have, see EveryiPad.com's iPad Identification section.

Can the iPad models be used as an external display for a Mac?

Officially, the iPad models cannot be used as an external display for a Mac, but as first spotted by Gizmodo, there is an iDisplay application that essentially "fakes" using the iPad as a second display on a Mac via a VPN server.

Can you make phone calls with the iPad?

No. The iPad models do not have the capability to make mobile phone calls. It is possible to use a VOIP application, like Skype, however.

Do the iPad models support Bluetooth?

Yes, all iPad models support Bluetooth, although the version supported is different for different models.

The original iPad models and the iPad 2 models support Bluetooth 2.1+EDR. The iPad 3rd Gen models, the iPad 4th Gen models, and the iPad mini support Bluetooth 4.0.

How much internal storage do the iPad models have? Can storage be expanded? Does the iPad have a MicroSD slot?

All iPad models have either 16 GB, 32 GB or 64 GB of storage which cannot be expanded. No iPad has a MicroSD slot.

For readers not familiar with the MicroSD standard, it is a tiny flash memory card -- "about the size of a fingernail" -- designed for mobile devices to hold "music, movies, video clips, pictures, ring tones and more". For more information regarding the history of the standard, please refer to PhoneScoop.