I'd like to know, if I download mac osx from the app store, will it install it ? I just want the dmg file. Don't want to install it... Thanks and sorry for my bad english.
When you download a copy of OSX from the app store, this will download the Package onto your machine (usually placed in either your Download folder or Applications folder). From here, you can gain access to this package and create a bootable device with it, or do with it what you will.
So in short, No. Downloading OSX from the app store does not install it.