http://www.alislam.org/ and http://www.aaiil.org/

1. The first one is, by far, the largest one. They believe that Ahmad is a minor prophet (a non-law-giving prophet). The second group believes that Ahmad is a reformer but not a prophet of any sort. There is also a long history of considerable antagonism between these two movements over this issue.
   
2. The Ahmadiyya Muslim Community (the largest group) believes in the prophethood of Ahmad. The Lahore Ahmadiyya Movement for the Propagation of Islam has a more or less traditional Islāmic view of Muḥammad as the Seal of the Prophets.
3. The Ahmadiyya Muslim Community has its own caliphate. The caliph is invested with certain interpretative authority. However, when the caliph interprets, he is obligated to consult with others. The Lahore group has an emir (an elected president) instead. (In the Ahmadiyya Muslim Community, national presidents are called emirs.)
   

Here is an excellent discussion on why jihād is not holy war:

http://www.aaiil.org/text/articles/others/truemeaningjihad.shtml

Musa

It would not have been possible for me to have attained this grace if I had not followed the footsteps of my lord and master, the pride of all the prophets, the best of mankind, Muhammad, the chosen one, peace and blessings of Allah be on him. Whatever I have achieved, I have achieved by following him, and I know from verified reliable experience that no man can reach God and obtain a deeper understanding of His ways without following that Prophet, may peace and blessings of Allah be on him.

Now, let me also make it known that the very first thing you are rewarded with, after having completely submitted yourself to the instructions and teachings of the Holy Prophet Muhammad, is that you are granted a new heart which is always rightly inclined, that is to say, a heart which has turned cold upon the love of this material world, and instead it begins to yearn for an everlasting heavenly pleasure. Having achieved this desire, this heart is now fit to receive that perfect and purest love–the love of God. Because of your complete obedience to him, all these blessings are bequeathed to you as his spiritual heritage.