ISIS is an English translation of the acronym in Arabic for Al-Dawla Al-Islamiya fi al-Iraq wa al-Sham, or the Islamic State in Iraq and al-Sham.
The organization has said its goal is to form an Islamic state, or caliphate, over the entire region, stretching from Turkey through Syria to Egypt and including the Palestinian territories, Jordan and Lebanon.
Some think ISIS flows better as a word in English. It also happens to be the name of one of a goddess of ancient Egypt.
CNN has been referring to the organization as ISIS, shorthand for the Islamic State in Iraq and Syria.
Arabic speakers say al-Sham can be translated to mean the Levant, Syria, greater Syria, and even Damascus.