Al Qaeda ("the Base") - alternatively spelled al Qaida and sometimes al Qa'ida is the catch-all term used in the West when dealing with so-called "Islamic" terrorism (as distinct from say, Christian, Jewish, Bhuddist , Catholic, Protestant etc etc forms of "terrorism"). To the extent that it ever had any genuine terrorism-connected meaning - which is debateable - any such meaning has been transformed into little more than a knee-jerk trigger word meaning something like "Really scary evil MUSLIM baddies"; in much the same way that the word "Communist" was also transformed. At a subliminal level, the effect of this transformation has been to demonise Muslims in general and it is arguable that that has been - and remains - the precise intention of the arbiters of real power in the West.
Wikipedia on al Qaeda
Wikipedia (on behalf of the "Official Narrative") defines al Qaeda thus:
.... a militant Islamist group founded sometime between August 1988 and late 1989. It operates as a network comprising both a multinational, stateless army and a radical Sunni Muslim movement calling for global Jihad. Most of the world considers it a terrorist organization. 
... and it continues with the standard shibboleths - having by now acquired the status of revealed truth - of the carnage "al Qaeda" has wreaked and plans to wreak. It is a good and useful work of reference - provided 'official narrative' blinkers are removed. All this requires that reasonable efforts be made to filter the copious facts listed, through the eyes of the countless millions Middle-Eastern and Central-Asian Muslims that have been on the receiving end of invading Western armies.
The origins of al Qaeda
One of the best expositions of the origins of al Qaeda was provided in an interview with Pierre-Henri Bunel and published in Global Research in 2005 . The interview transcript is also available on Wikispooks. Brunel was a former Major in French Military Intelligence and concludes his article thus:
"The truth is, there is no Islamic army or terrorist group called Al Qaida. And any informed intelligence officer knows this. But there is a propaganda campaign to make the public believe in the presence of an identified entity representing the 'devil' only in order to drive the 'TV watcher' to accept a unified international leadership for a war against terrorism. The country behind this propaganda is the US and the lobbyists for the US war on terrorism are only interested in making money."
A satirical view
From the Wikispooks blog: 
Arabic, like English and most languages, has its collections of homonyms and it appears that “Toilet” (loo, khazi, WC, gents, john etc etc.) is a particularly populous one – especially since they have to cater for the Western fashion of sitting on a seat with a hole in it, rather than squatting.
And guess what? “al-Qaeda” is one of them – and the seat-type Western one at that!
So question: Can you imagine a group of terrorists styling themselves “The Red Toilet Faction”, “The Toilet Brigades”, “The Irish Republican Toilet” ? - Hmmm; me neither. It sticks out like the bulbous red backside of an Orangutan you might say – and sort of gives the game away.