An egg shaker or ganzá is a hand percussion instrument, in the idiophone category, that makes a noise when shaken.
It is partially full of small, loose objects, such as seeds or beads, which create the percussive sounds as they collide, both with each other and with the inside surface of the container.
The egg shaker is a Latin American instrument, cheap to buy and relatively simple to play.
Another sound can be made by holding the shaker in the palm of the hand tightly, then opening it whilst shaking it up and down.
Egg shakers are available in a number of colours, and are sold in most music shops at a reasonably low price, due to the use of inexpensive materials like plastic and seeds.