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

No. The "MagSafe" or "MagSafe 2" 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.

The "Mid-2012" MacBook Air models have a "MagSafe 2" power adapter and can be powered by its own power adapter or the "MagSafe 2" power connector from a Retina Display-equipped MacBook Pro. The MagSafe 2 power connector is not backwards compatible with earlier power adapters, but an earlier MagSafe power adapter can be used to charge a MagSafe 2-equipped MacBook Air with a US$10 adapter from Apple (MD504ZM/A).

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 "Mid-2011" models, Apple again provided it as a US$29 option.

For the current "Mid-2012" MacBook Air models, Apple offers a Thunderbolt to Gigabit Ethernet adapter for US$29.

Is an external modem available for the MacBook Air?

Apple used to offer an external modem. 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" and later versions of the operating system do not support modems at all.

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

Please note that the current "Mid-2012" MacBook Air models support a newer Bluetooth 4.0 standard.

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.