Tapping is a game mechanic which is used in many ways across the game.
Single Tapping Edit
Zomblin Caves, Decayed Logs, Demon Gates and Lifeless Rocks can all be attacked by single tapping them. If a dragon is available, it will come and start attacking. Multiple taps will summon several/all Dragons.
Floating objects Edit
Tapping floating objects will make them drop to the nearest tile possible, if the map isn't full.
Gathering Products Edit
Fruit Trees, Midas Trees, Graves, Magic Coin Storage, Stone Storage, Wonders, Nests, Fountains, Cloud Mountains, Events Objects, Bushes,Cabins, Loot Orbs, Idols, and Unearthed Skeletons, all can be tapped for their products.
Opening Chests Edit
Every chest requires tapping in order to open it (and, sometimes there is an additional gem fee, see Dragon Chests).
Consuming Stars Edit
Collecting Objects Edit
Coins, Bricks, Gems, Life Orbs and Bonus Points all need to be tapped in order to gather them. Higher levels of those object(with Bonus Points as an exception), however, will have a Tap Confirmation Message when are tapped (if that option turned on at the Option Menu), and when that message (or the button on the lower left hand side) is tapped, they will be collected.
Startling Zomblins in Caves Edit
Make it Rain Edit
Activating Heal Extenders Edit
Though Heal Extenders would be activated on their own after sufficient time have passed from the unlocking moment, tapping them would activate them immediately.
Double Tapping Edit
Harvesting an object can be performed by double tapping the object. If any dragon is available and free (not sleeping/doing something else which it autonomously chose to do) it will come and harvest the wanted object.
Building a building can also be perfomed by the same manner as harvesting, double tap the construction site, if a dragon is available, it will come and start building.
Quadruple (4x), Sextuple (6x) and Octuple(8x) Tapping Edit
Some harvestable objects can have more than one dragon harvesting them in the same time. When such an object is presented, it can be quadruple tapped for calling two dragons to harvest it. If three dragons can harvest at the same time, a sextuple tap can be made to call all three. If four dragons can harvest at the same time, a octuple tap can be made to call all four.
Tap Protection Edit
In the game's Settings there's an option called "Tap Confirm". When this option is turned on, when tapping a valuable consumable object, an alert of "Confirm Tap?" would appear above the object instead of gathering it. Only after tapping the "Confirm Tap?" button, the item would be gathered. It is applies to high levels of Stone Bricks, Magic Currency, Life Orbs, Dragon Gems, Dragon Star, event points objects and various chests.
In short, this option prevent accidental unwanted taps on valuable items.