This is the Ganesh Aarti, a prayer which is utilised after a Ganesh puja (ritual) is conducted.
It usually signifies the end of the ritual and most times comes right before the Shantipath (prayer of peace and well being) is said. One would take a thalia (sacred prayer tray) and place in the centre or close to the end of the thalia a lit deya or lit piece of camphor. The thalia may contain a number of additional items such as flowers, sweets, incense and any other offerings (post havan) to be made to Ganesh. The thalia is then, with the flame facing Ganesh's image, waved in a clockwise motion whilst the Aarti itself is being chanted.
After this is done the flame is usually passed around to all who attended the puja to receive its blessings.
Aarti literally means to wave a sacred flame before an image of Bhagavan.