A priest performing puja at the Swayambhunath temple. Puja is a prayer ritual performed by Hindus to host, honour and worship one or more deities, or to spiritually celebrate an event. The word comes from Sanskrit, and means reverence, honour, homage, adoration, and worship. There are many things that are needed for the ritual but water, flowers, fruits and rice are the main ingredients. Incense sticks, coins, a bell and different kinds of vessels are also used.
You can see a vajra on the sacred scripture. Seems like the priest uses it as a bookmark here.