Recalling a dragon sends it back to Dragonverse, meaning you no longer own that dragon. In return, you will receive Orbs of that dragon. The higher the level of the Recalled dragon (maximum level 30) or the more Empower stars it has, the more Orbs you will receive. These Orbs will appear in your Tree of Life.
Please note that only duplicate dragons can be Recalled and you will lose any Dragon Master Points associated with the Recalled dragon.