Answer 1
There is, perhaps, no term today that is more misunderstood than the term "jihad". Nowadays, the word jihad has solely come to signify "holy war", terrorism, or the mass murder of innocent people. However, what is jihad really about and what is its correct meaning? The term jihad is in fact derived from the Arabic verb "jahada", which linguistically means to strive or struggle. In Islam, however, jihad means to exhaust utmost effort striving to please God. This, unsurprisingly, includes fighting, as fighting is a form of struggle. In fact, majority of the time the term jihad is mentioned in the Qur'an it means "fighting in the way of God" (for His sake), and to make His Word the highest. The one who engages in jihad is called a mujaahid; the plural is mujaahideen.
Jihad is a very important part of Islam. Unlike Christians, Muslims do not believe in the idea of "love thy enemy" or turning the other cheek when we are attacked. Instead, we believe in the divine principle, "fight those who fight you." This general guideline and rule agrees with our human nature and survival instinct. That is because it is only natural for one to retaliate against aggression and defend one's life, property and wealth from any external attack.
Sadly, this basic human right - the right to defend oneself - is nowadays denied to Muslims by modern-day democracies and so-called free nations, such as Britain and the USA. This is clearly evident in the fact that Muslims in Afghanistan, Iraq, Palestine, Chechnya and Kashmir who are resisting the brutal occupation of their lands are continually branded and portrayed as terrorists and violent extremists by Western powers.
On top of this, any Muslim in the West that has the fortitude to condemn the evil actions of Coalition forces is similarly branded as a "terrorist sympathiser" or accused of "glorifying terrorism" for believing in the right of Muslims to defend their land from occupation. It is not even allowed for us to discuss the causes of 9/11 or 7/7 - in order to gain lessons - without fear of being labelled a terrorist fanatic.
The irony of this situation is that if tomorrow Britain is under occupation, every Briton would consider it their right, without any question, to fight for their country and defend their land, even if such actions were deemed terrorism by other nations.
So, in summary, jihad does not translate as "holy war" or the killing of innocent people. It is to strive, with utmost effort, to please God and fight in His way. It is famously reported that Prophet Muhammad (peace be upon him) said, "The best form of jihad is to speak the truth in the face of a tyrant ruler."(Abu Daawud and Al-Tirmidhi)
The greatest tyrants today are those who prefer the rule of man over the laws of God (Sharia law). Jihad and the establishment of Sharia law on earth are the only two things which will unite all people, of all races, and rid the world of oppression, poverty and corruption for good.
Answer 2
Jihad is a part of the religion Islam. The word means 'struggle', even though many parts of the media report that it means 'holy war' or similar things so that they have something to write stories on.
Jihad is completely different from terrorism. Even though organizations like al-Qaeda claim that they are following the Jihad rules, they are not.
Answer 3
There are two forms of jihad. One is an internal struggle to be true and faithful to Islam amidst all of the struggles and difficulties that the world presents. The second is the command to rise militarily in defense of Islam when Muslims are under attack, especially from non-Muslims. This second form of jihad is popularly considered the "holy war" type of jihad.