The Illuminati is an organisation created, about 3years ago iirc; in germany. The founder wanted to create a 'super group', who could solve all of the worlds problems with thier intelligence and science.
Hense logo being an Eye, called the ASE (All Seeing Eye) inside a pyramid top that hovers above the rest.
It is suppose to depict the top minds being able to see and know all.
The group has been underground so long that no-one knows if they currently skill exist, but it is rumoured that they not only still exist but they currently work around the world in order to benifit thier own personal gains.
Some people believe that every war, country conflict, oil prices, etc.. are controlled by these 'men' (never a woman in the ranks which is quite odd), and so is everyone fate. Not to mention they believe that they have some sort of survailance service which can pick up when your talking / writing about them and they can monitor it.
Personally, while I don't doubt there is still the organisation, and it is still underground due to the many years they had to be because of the threat of death.. I somehow doubt that they are acting as 'the worlds masters'.
Especially when I hear that people like G.W.Bush Jnr are part of them. The whole point in the Illuminati was to only accept the best & brightest... Bush gets trapped if he puts his head inside a bag of doritos!
That's pretty much a bland overview of it all, could try and look for a more historically accurate version. I sort of like the idea of the Illuminati, in terms of a mythical entity.. you shouldn't really try to take it seriously like the conspricy theorists.