Maracas

The maracas is basically a calabash (or gourd) still containing its dry seeds inside. The instrument is shaked (also called a shaker), and the seeds or other small objects bump and scrape against the inner wall of the cavity, creating sound. The body of the instrument serves as amplifier. Modern plastic variations of the instrument are also made.

Some gourds have a natural "handle". A handle is added to those who do not have natural ones.

Source: http://www.seedman.com/image/rgs002.jpg