U.S. President Barack Obamaon January 30 when he acknowledged that the United States’ has used unmanned aircraft -- known as "drones" -- to attack high-value terrorist targets on Pakistan’s territory.Now that President Obama had confirmed such attacks take place, RFE/RL presents this quick explainer to cast some more light on these mysterious planes.A drone, or unmanned aerial vehicle (UAV), is a pilotless plane which can be guided by remote control, or can navigate automatically based on pre-programmed software.Drones, which come in numerous shapes and sizes, have a wide range of potential civilian and scientific uses, including law-enforcement and industrial monitoring. But they are overwhelmingly used for military purposes, mainly for reconnaissance and combat operations.Drones have been developed for decades by various countries. They came to their recent military prominence due to two factors: (1) technological advances allowing unmanned flying objects to be accurately guided over large distances and (2) better intelligence gathering on the ground, which makes it possible to pinpoint and strike high-value military targets while keeping civilian casualties and other collateral damage as low as possible.The administration of U.S. President Barack Obama began using them on a large scale against militants and Al-Qaeda terrorists in the tribal regions along the Afghan-Pakistan border.Based on unofficial accounts, 45 suspected U.S. drone strikes were reported in Pakistan's tribal belt in 2009, 101 in 2010 and 64 in 2011.Many countries are attempting to manufacture drones, but most of them are either technologically unsophisticated or are being used strictly for civilian purposes.The United States and Israel are the two most important manufacturers of military drones.The United States is both the largest producer and the most frequent user of the aircraft.The U.S.-made Predator (which costs $4.5 million-$11 million per unit) or the larger, more expensive and more advanced Reaper ($30 million per unit) are the best-known UAVs.The American military now has some 7,000 aerial drones, compared with fewer than 50 some 10 years ago. The Pentagon has asked Congress for nearly $5 billion for drones in the 2012 budget.Israel was the first country which developed military drone technology after the 1973 Arab-Israeli war, during which its air force sustained large losses.It manufactures a wide array of drones, including one of the largest and most advanced models in the world -- the Heron TP Eitan, which costs an estimated $35 million.With a wingspan of 26 meters it is the size of a Boeing 737 passenger jet and can reach an altitude of 12,000 meters.It can also stay in the air for more than 20 consecutive hours -- making it possible for Israel to fly surveillance missions above Iran.Israel is also a top drone exporter. Despite a recent deterioration in diplomatic relations with Israel, Turkey is reported to use Israeli-made drones in surveillance operations in northern Iraq.Israel has reportedly sold components and technology for as many as 60 of its Orbiter 2M and Aerostar drones to Azerbaijan, one of Israel’s closest Muslim allies.Intelligence gathered by surveillance drones is reported to have played a crucial role in the success of the special forces’ killing of Osama bin Laden in May 2011.U.S. drones have been employed successfully against Islamic militants in Somalia, and Al-Qaeda operatives in Yemen.In two spectacular attacks, U.S. drones killed militant cleric Anwar al-Awlaki and his son, Abdulrahman, with two successive strikes in Yemen in September and October 2011.Most recently U.S. officials have revealed that unarmed drones have been used to protect American diplomats, including those in Iraq.In December 2011, Iran claimed to have brought down and captured a U.S. drone and rejected America’s request to return it.However, it is not clear if and how Iran actually brought it down or if they are truly in possession of the wreckage.Iran claims to have successfully tested a long-range combat drone called the Karrar in 2010. According to Tehran, the aircraft is four meters long, and has a range of 1,000 kilometers -- which puts it within striking range of Israel.Nuclear archrivals Pakistan and India also say they are in possession of combat-capable drones, although it is unclear how developed or how efficient their UAVs are.Many other countries, including world powers Russia and China, have been trying to manufacture deployable drones for a long time. But technological difficulties and a lack of accurate intelligence gathering capabilities imposes limits on the effectiveness of their use.It is not just nation states that have shown an interest in drones. There have been unconfirmed reports that Hizballah used a drone in the 2006 war in Lebanon. Al-Qaeda was also once reportedly looking into the possibility of using UAVs.RFE/RL's Azerbaijani Service contributed to this report