In Arabic, the word jihad translates as a noun meaning "struggle".
In other words, jihad is the struggle against, or resistance to, something for the sake of a goal.
Actually, jihad is an internal struggle to maintain the true faith in 'God',which is the opposite of all types of religious faiths in this world.
Koran is a Spiritual book, which is NOT written to start a new religion like Islam,
but to fight against many traditional superstitions rooted in all religions in this world.