The Islamic State in Iraq and the Levant, (ISIL), is an armed group active in Iraq and Syria seeking to establish an Islamic caliphate.
With thousands of Arab and foreign fighters under its wing, it has emerged as one of the most powerful such groups in the region.
An off-shoot of al-Qaeda, the group has attacked rivals and killed hundreds for violating its strict interpretation of Islam.
Despite the Iraqi army's efforts to dislodge the fighters, the group controls parts of two of Iraq's biggest cities in Anbar province, most of Mosul and several neighbourhoods in Kirkuk province.
ISIL also controls parts of northern Syria, including their stronghold city of Raqqa, and are fighting rivals Al Nusra, for the oil-rich city of Deir az Zor.
Some suggest it relies on hefty donations by individual sympathizers while others claim it has strong backing by regional states and their intelligence services.
ISIL's real goals and backers remain unknown, but their attacks have now caught the world's attention.
Al Jazeera's Omar Al Saleh reports.
Source: Al Jazeera