what does .dmg mean?

The dmg extension stands for device i mage, and these files are basically drive container files. Using them decreases the size of the file you need to download to get an application; they also include checksum verification, which will tell you if the file was damaged in transit, and can be opened directly in the Finder, which is more convenient than other compressed file formats.

(14665)

Indeed. Opening the 'dmg' image will create a new drive in the finder.

Think of it as putting a cd-rom in the drive. The contents of the drive then appears.

If it's an application, and all you see is the application icon (and maybe a 'ReadMe' file), you can usually just drag the icon to the application folder.

Sometimes an application needs to be installed, and in this case the icon will usually have a '.pkg' extention, or will look like a box being unpacked.

Once you've installed your app, you need to 'eject' the disc image (just click the little eject button next to the dmg in the finder), then you can trash it! (Or, if you're like me, save it for the future in case you need it again)

As Mr Lizard pointed out, if the dmg contains an app that you are installing, be sure to drag the app out of the window and into your Applications folder before running it. If you try to open it from within the dmg window, strange things can sometimes happen.

Regards,
Steve M.

Yep, forgot to mention that bit!! Always drag the app out of the dmg first.

Incidently, you don't need to drag it to the applications folder if you don't want to. Any folder will do, even the desktop, but it makes sense to keep them in the app's folder.