The terms ISIS and ISIL are often used interchangeably when referring to the terrorist group, but they are not the same.
ISIS, which stands for Islamic State in Iraq and Syria, originally began as an offshoot of al-Qaeda. It got its name after it invaded Syria in 2013.
ISIL, which stands for Islamic State of Iraq and the Levant, refers to the terrorist group spread throughout the Middle East. The Levant is a geographic term that refers to Syria, Lebanon, Palestine, Israel and Jordan.
President Barack Obama referred to ISIL when he addressed the nation last week.
"The threat from terrorism is real, but we will overcome it. We will destroy ISIL and any other organization that tries to harm us,” the president said.