I tried Launchpad first time today and went through the common modifier keys & their combinations to see if some hidden options appear.
When I pressed ⌥ ALT all the apps started wiggling. What does it mean?
Wiggle is the edit mode. (so you can delete or uninstall the apps that came from the app store)
Holding alt is the quickest way to enter edit mode.
If you click and hold them they also start wiggling. It lets you drag them around, to re-arrange them, and also delete apps from the Mac App Store.
When they are wiggling you can rearrange them AND delete/remove apps that you yourself have downloaded. System apps (like iOS) cannot be deleted.