The MacBook Air is a laptop and is a normal full featured computer, running a fully featured MacOS like the other laptops that Apple make's. It is not a "dumbed down" or "minimized" Netbook. There is nothing to jailbreak on a Mac Laptop.

"Jail-breaking" refers to "Hacking" a tablet or smartphone "iOS" like the iPhone, iPad, etc.

To Jailbreak something means to bypass (or unlock) the security features of the OS to run unauthorized applications, or to use another cell company. You can then download ANY games or applications that you could not other wise down load because of the 'Lockdown' status the manufacturer puts on it's products.

They do it to keep poorly written applications, etc, from making the device run slow, using excess battery life, possibly getting malware or a virus and then the customer blaming the manufacturer because the device is crashing or running very slowly. Use caution and common sense if you intend on jail-breaking a device.

Update: This answer was written sometime around 2008 and is, at the time of this comment, at least six years out of date. In the computer world, this is a long time in which many things can, and have, happened. The spirit of the answer is roughly correct, but the many details are different.

While I could simply say "yes, Macs are better than PCs," the question is actually difficult to answer since in truth it depends largely both on personal preferences and personal needs. And though I am of the opinion that Macs are significantly superior to PCs and that Mac OS X is significantly better than Microsoft Windows, to state that as fact would be unfair to those with the opposite opinion. Rather, I will attempt to state the differences themselves and let you decide. Nevertheless, I do not want to appaer as a closed minded Mac fanboy simply as a result of my opinion -- in reality, I frequently use XP and have had experience with Windows Vista, not to mention extensive experience with Windows 95, 98 and ME. So onto the answer...

In terms of hardware, Apple Macs (including the various desktop and notebook Macs) tend to use higher quality casings, parts, and hardware than other PC brands. (For example, longer lasting and higher performing Intel processors rather than AMD processors, actual aluminum and steel metal parts rather than painted plastic, and solid glass screens rather than a sheet of gloss plastic.) Webcams, the Apple Remote (for use with things such as the bult in Front Row media center or PowerPoint presentations), internal serge protectors and hard-drive-protecting motion sensors are also commonplace. Macs also frequently make use of magnets rather than clips and other breakable parts (like for securely closing a laptop's monitor or affixing the Apple Remote). Macs are also sleek and are the hardware is nicely integrated with the software.

However, Macs lack of some useful things many PCs have, such as built-in storage card readers or fingerprint security.

Many PC advocates have also made the argument that PCs are cheaper than Macs. However, I would argue that, while inexpensive PCs do exist, they typically lack the high-quality hardware present in Macs. Furthermore, PCs similar to Macs (for example, the Dell XPS laptops or the all-in-one form factor PCs) tend to cost more than Macs and still include slower processors or have other drawbacks.

The prime focus of the argument is whether Mac OS X or Microsoft Windows is better. I will say Mac, citing things such as its resistance to malware, high performance, high reliability, streamlined user interface, and built in tools which can do things such as burn bootable DVDs from ISO images, burn playable DVDs from a VIDEO_TS folder, save any printable document as a PDF, other image conversion and manipulation tools, the bundled iLife software, and the fact that you don't need to activate it when you set it up. Other advantages are the automatic Time Machine backup and the selective restore tool, comprehensive Exposé, Spaces and Widgets time-saving tools.

However, for fairness's sake, I will state the arguments of the PC-supporter. Though the software available form Macs has become very high, there is nevertheless more software made for Windows than Macs. Other arguments for PCs include stating that Macs only seem impervious to malware since all malware is targeted at Windows and that Windows performance is not really worse than that of Mac OS X, two statements I would contest.

Windows' advantages, specifically that of Vista (the most recent version of Microsoft Windows -- one that I would point out has its drawbacks), would include the presence of a Media Center (in the more expensive versions) for use with a TV or for viewing other media on the computer, search-as-you-type in the start menu, and desktop Gadgets. (It should be noted that these new features are also found in Mac.)

So now that I have detailed some differences, it is up to you to decide what you prefer or how either one would best suit your needs. If you are often required to use obscure software and you can't spend more than $500 on a computer, PCs may be the way to go. Or if you are a graphics designer and need a good, quick and reliable for your work, a Mac may be the way to go. Which one is better is up to you.

Steve Wosniak... did the interface for sure

DMG is a file type. You don't install a DMG, you open it. Maybe there is something inside the DMG that can be installed, maybe not. It is a common way to send many kind of files. It is a bit like .sit or .rar.

You can make your own DMG files and save things inside them, and send the dmg to your friends. Use Disk Utility to make DMG files. The DMG size is selectable and can be as big as your free memory. It will appear on the desktop. You can put a password on it, but don't forget it! If you do, you won't be able to open the DMG!

To open the DMG you made, just click on it. A disk Image will appear on the desktop just like a hard drive.

Drag or copy files there. Eject it. The DMG file is still on the desktop. It is a file that you can email or copy to an external drive. Everything that you put in the disk image will actually be in the DMG file. If you don't want the DMG any more, drag it to the trash.

Cool!