Hello Juanmitra, welcome to Philmug. When you download mac software, if it has a .dmg extension, it means its a disk image. When you double click on it, it'll mount on your desktop and inside you'll find the installer which you double click to begin installation. If you get a .bin, .hqx, etc., its a compressed file and you'll need to download the free Stuffit Expander to decompress the installer file/folder. If its a .zip, you just double click it and it'll uncompress automatically.
More often than not, it's the actual application that's in the disk image (or .zip file, etc.). In that case, just drag the icon into your Applications folder in Finder and you're good to go. It's then safe to unmount/eject the disk image and trash it. [Edited on 8-11-2005 by PatrickGaerlan]
So after the App has installed, I can drag the .dmg file to the trash? It's just an installer? And I don't have to drag the .dmg file to the Apps folder to use it?
as kenneth said, if the dmg file (after mounting) contains an installer, just follow the instructions and after the last step (which is usually pressing the Finish button), the app is already installed and you can already trash the dmg file.. in the case of patrickgaerlan's post, once you drag the app file into your applications folder, it's already installed and you can trash the dmg file too.. unless of course you would want to keep them for future use..