Is the "MagSafe" power connector that ships, or shipped, with MacBook Air models also compatible with the MacBook and MacBook Pro?

No. The "MagSafe" power connector that has shipped with each MacBook Air model only provides 45-watts of power, and as such, cannot power a MacBook or MacBook Pro model, which all require more power.

Additionally, the "MagSafe" power connector for the original, "Late 2008" and "Mid-2009" MacBook Air models is rotated 90-degrees to save space. A "regular" MacBook "MagSafe" power connector will provide power to these earlier MacBook Air models, but it won't fit when the MacBook Air sits on a flat surface. On the other hand, a regular MacBook "MagSafe" power connector can provide power to the "Late 2010" and "Mid-2011" MacBook Air models.

Does the MacBook Air really not have an Ethernet port? How can you connect to wired networks?

MacBook Air models really do not have an onboard Ethernet port. Apple instead offered an external Apple 10/100Base-T Ethernet adapter that connects via the sole USB port on the MacBook Air for US$29 for the "original" and "NVIDIA/Late 2008" models. For the "Mid-2009" models, Apple provided the external Ethernet adapter free of charge with the system. For the "Late 2010" models, and continuing with the current "Mid-2011" models, Apple again started providing it as a US$29 option.

Those who require Gigabit Ethernet capability -- or who are disinterested in carrying an adapter to connect to wired networks -- would be better served by a MacBook or MacBook Pro.

Is an external modem available for the MacBook Air?

Yes. Just like all the other Intel-based Macs, Apple does not offer an internal modem with the MacBook Air. However, an external Apple USB Modem (56.6k v.92) originally was offered for US$49. Apple no longer sells this modem, but third-party ones are available that are compatible with MacBook Air models running Mac OS X 10.5 "Leopard" or Mac OS X 10.6 "Snow Leopard". Mac OS X 10.7 "Lion" does not support modems at all.

What is Bluetooth? What is the difference between Bluetooth 2.0+EDR and 2.1+EDR?

For those who have yet to use the ubiquitous Bluetooth technology, Apple originally described it as:

Open specification that enables short-range wireless connections between desktop and notebook computers, personal digital assistants, mobile phones, camera phones, printers, digital cameras, keyboards and even a computer mouse. Bluetooth wireless technology uses a globally available frequency band (2.4 GHz) for worldwide compatibility.

In a nutshell, Bluetooth technology unplugs your digital peripherals and makes cable clutter a thing of the past. . . You can link your Palm OS-based handheld device [or more modern iPod touch], mobile phone and other peripherals with Bluetooth technology -- and do it wirelessly, within a 30-foot range.

Bluetooth 2.0+EDR and Bluetooth 2.1+EDR are quite similar, but the newer 2.1+EDR standard offers improved security, "pairing" (meaning that it is simpler to connect devices to one another), and power optimization.

For more details regarding Bluetooth 2.1+EDR, please refer to The Unwired and GearLive.