When you drag and drop a folder onto the dock, the icon on the dock of that folder is an alias back to the original folder location. The default is to make that folder dock icon a stack. When you drag and drop files into the original folder, the dock alias of that folder (the stack) bounces and you now see a fan fold of the files that were dropped in the original folder.
By example, I created a new folder in my login directory. Called it Foobar, and dragged it to the Dock right next to the Trash icon. By default, it made itself a stack. I now dragged three arbitrary files onto the original folder. The Foobar dock icon bounced once. When I clicked on it, a new stack revealed the files that were copied into the Foobar folder. The result looks like this:
If you were to click on any one of these files, it would be opened by the default application for that file type. If one of these had been an installer, you could click on the installer and it would open in a window as you would expect an installer to do.