There are two kinds of jihad, the major jihad and the minor jihad.
The Major Jihad: (Jihad Al-Akbar)
This is the struggle against one's inner self (nafs) to subjugate and control one's passions and carnal desires. The base self (nafs-e-ammara) must be controlled by the conscience (nafs-e-lawwama), and only when one succeeds in this struggle does one attain the perfect self, the self at peace with itself (nafs-e-mutmainna). To those who attain this state, the God says:
" O the soul at peace, return to your Lord, pleased with His good pleasure AND enter into the company of My true servants. Enter the Garden !." (LXXXIX:27-30).
The Minor Jihad (Jihad Al-Asghar)
This means to struggle for Islam. Not for extension of boundaries, not for personal glory, not for the glory of any tribe, community or nation, but for the defence of Islam and the protection of its values. Such a struggle can take many forms, through the use of pen, through the use of tongue or through the use of the sword. This last form is often referred to in the Quraan as Qitaal (warfare).
In the Shiah theology, a general qitaal can be declared only by an Imaam. A mujtahid has no authority to summon Muslims to a jihad involving qitaal.