Al-Qaeda meaning the "base" is used to denote stability and
steadfastness of purpose. In the
afghanistan war against
Russia, it and other groups like it were responsible for pushing the
red army back over the border and freeing the populaton from the threat
Soviet rule. The Soviets for their part threw everything they had into the war for over a
decade and were still unable to
destroy them or break their
spirit.
It is worth noting that they were one of only two superpowers in the world at the time, and had far more manpower, and armed forces than the poor untrained Afghans at the time, and they still failed. Almost all of the military equipment in Afghanistan today is there because it was captured from the Soviets during the war of liberation. In this respect the name is quite apt. The other meanings of the word "base" don't really apply to this group, as the word only has those negative connotations in English, and in Arabic, the sense of the word is clear and unambigous.
The current leader of Al-Qaeda, Osama Bin Laden was a fighter in the war that kicked the Russians out of the country, and his leadership and intelligence naturally brought him to the head of the force he was fighting in. This may have been helped by the fact that his was Saudi, and his family rich and well connected, giving him an excellent formal education accompanied by religious tuition from a young age.
His comittment to the liberation of Afghanistan turned into the wider goal of liberation of Muslims from the influence of the West, and he saw the Gulf War as an excuse for installing and manning military bases throughout the Middle East, and especially the Holy Land of the Muslims, Osama's native Saudi Arabia. Since that time Al-Qaeda moved from being an almost conventional fighting force of mujahideen to the roles of freedom fighters on an internation stage.
The "quiet war", as it has been called by many analysts has in the main involved financial assistance and tactical training of Muslims in those countries where the regime is harsh and oppressive of those following Islam, this includes of course Israel, and many north african states, not excluding Sudan.
The move from a united if flexible fighting force to that of freedom fighting changed the structure of the organisation dramatically. As the West's influence was manifold, and spread over the globe, the organisation had to follow suit, sending people to the appropriate locations, and as most of the acts of repression occurred through the routes of policy and through covert assassinations and torture, the units sent had to be trained to conceal themselves, and intervene whenever possible to save lives, and bring those under attack to safety.
Note: These sorts of operations are rarely reported in the media as it is against the interests of the governments in control, even though they are common in Islamic circles.
An example is Hamas, which while widely reported as a terrorist organisation in the West is actually responsible (in addition to it's freedom fighting activities) for building hospitals (in the form of closely knit groups of clinics), schools, giving out blankets for the homeless and setting up soup kitchens for those people who have been badly treated by the occupying regime in Palestine.
The Al-Qaeda organisation, thus changed into the Al-Qaeda group, or as the west calls it "network". Although this isn't strictly correct, a network implies regular communications between disparate units, and the organisation is structured much more loosely and fluidly than that, with each unit being independent of one another, and knowing very little if anything about members outside the unit.
Most of Al-Qaeda's operations are intelligence gathering, training, relief supplies, and responses to those brutal violations of human rights that America and the UK sanction for the the rest of the world, but not their own people. Al-Qaeda has been responsible for actions against repressive regimes throughout the last two decades, mostly peaceful propaganda, except in rare cases of extreme provocation such as Bosnia, Somalia and Chechnya.