The Arabic, the term jihad means "to strive," and "to fight." In Islam, the verb carries two levels of meaning that affect the individual Muslim.
First, the individual Muslim must strive (jihad) against his flesh. Surah al Tawbah 9:20 says, "Those who believe and suffer exile and strive [jihad] with might and main in Allah's cause ... have the highest rank in the sight of Allah." In this dimension, the jihad is against oneself. The Muslim must learn to control his sinful impulses and desires. In this dimension, jihad is a means for the Muslim to earn salvation. The aforementioned verse ends with this promise, "they (who jihad with might) are the people who will achieve salvation."
Second, however, jihad has a corporate dimension. The Qur'an teaches that jihad is warfare in the cause of Allah. This fighting (also jihad in Arabic) is required for Muslims, even. if they do not want to do it (Surah 2:216). The nature of jihad is unambiguous in the Qur'an. Surah al Tawbah 9:29 says, "Fight [jihad] those who believe not in Allah nor in the Last Day, nor hold that forbidden which has been forbidden by Allah and His Messenger, nor acknowledge the Religion of Truth, from among the people of the Book until they pay the Jizyah with willing submission."
In this corporate dimension, jihad is clearly seen as warfare. Specifically, Islam teaches that jihad is fought against those who do not recognize Islam as the only truth. In the context of Surah 9:29, jihad's purpose is for either the conversion of the infidel, or the control of the non-believer. If a non-believer will not believe, he must pay a tax, called jizyah, as a sign of his submission.
Jihad as warfare has parameters in Islam. Muslims who are blind, lame, or terminally ill are exempt from holy war (Surah 48:17). Muslims must give a warning of four months (fatwa), telling the infidel to convert or surrender. After these "forbidden months," the Muslim warriors must "seize them, beleaguer them and lie in wait for them, in every stratagem of war" (Surah 9:1-5). Some Muslims cite Surah al Baqarah 2:256 ("there is no compulsion in religion") but earlier in that same ' chapter, Allah says, "and slay them whenever ye catch them and turn them out from where they have turned you out" (Surah al Baqarah 2:191). Once jihad begins, it must be fought until victory or the surrender of the unbelievers (Surah 47:4). The Muslim who dies in jihad is promised heaven (Surah 47:4-6).
Extracted from the Apologetics Study Bible.