Install icons on desktop

I've used macs for years, but never owned one until this year, anyways, i was wondering what those little harddrive icons are on the desktop after you install a program? i've deleted all of them, but could this cause issues? also why can you "eject" them from finder?

The harddrive icons are mounted disk images. When you download a .dmg file, the system can treat it exactly as if it was an actual disk and so mounts it like it would a CD or USB device. When you unmount it, the system simply closes the .dmg file and you can delete it, store it or whatever.

So, no harm done. Once you have installed the program (usually just dragging it to the Applications folder) those disk icons are just left overs - you can safely delete them.

ok thanks a ton!