The DualShock Analog Controller (SCPH-1200) is a controller capable of providing vibration feedback based on the on-screen action of the game (if the game supports it), as well as analog input through two sticks. The controller is called "DualShock" because the controller employs two vibration motors: a weak buzzing motor that feels like mobile phone or pager vibration and a strong rumble motor similar to that of the Nintendo 64’s Rumble Pak.

Source: Wikipedia, DualShock , available under the CC-BY-SA License.