Jihad is an Arabic word that means "striving" or "doing ones utmost". Within Islam, there are two basic theological understandings of the word: the "Greater Jihad" and the "Lesser Jihad". The Greater Jihad is the struggle against the lower self, the struggle to purify ones heart, do good, avoid evil, and make oneself a better person. The Lesser Jihad is an outward struggle, which may involve fighting against oppressors and aggressors who commit injustice. It is not "holy war" in the way a crusade would be considered a holy war, and while Islam allows and even encourages proselytizing, it forbids forced conversion.

Jihad constitutes a moral principle to struggle against any obstacle that stands in the way of the good. Jihad also includes the right, indeed the obligation, to defend Islam and the community from aggression. Throughout Islamic history, wars against non-Muslims, even when motivated by political and secular concerns, were termed jihads to grant them religious legitimacy. However, the form of jihad that involves fighting requires specific ethical conditions under which it is permissible to fight, as well as clear rules of engagement such as the requirement to protect non-combatants.

Jihad is a complex set of doctrines and practices that have changed over time and continue to evolve today. The Qurans messages about fighting and jihad are inseparable from its requirements of generosity and care for the poor. Jihad has often been a constructive and creative force, the key to building new Islamic societies and states. While todays "jihadists" are in some ways following the "classical" jihad tradition, they have in other ways distorted and perverted it.