What is RQ-4 Global Hawk drone, the US aircraft shot down by Iran?

The RQ-4 Global Hawk drone, made by Northrop Grumman Corp, is used for intelligence-gathering over water and coastal areas. It's designed to fly at high altitudes of up to 60,000 feet. It can fly for up to 32 hours and has a range of up to 12,300 nautical miles. Iran shot down a US RQ-4 Global Hawk drone on Thursday.