It's a sort of Lego-style approach to computing - usually supercomputing.
Grids connect up computers - usually not in the same building or even the same country - with the idea of joining up power and resources of disparate machines. The term 'grid', coined by Dr Ian Foster, refers to the idea of electricity grids - the theory behind both computer grids and electric grids being that you get power whenever you need it, with power going in from any number of disparate sources.
That's it, then? That's a grid?
Well, yes and no. Grids are still loosely defined and not even those working on them necessarily agree on what they are. For example, some business grids are used to connect up a load of PCs in one building. Some grid researchers consider that an intra-grid, not a grid proper, for example.
Grid - that's all about finding aliens, isn't it?
I suppose you mean SETI@Home - where people around the world contribute their spare computing power to analyse radio telescope signals in the hope of finding some extra terrestrial life. Some would say that's a grid though its creators say it isn't. Either way, there is more to grid than aliens.
A lot of the grid projects up and running at the moment are in academic or research institutions. The biggest grid working at the moment, part of the Large Hadron Collider, has over 6,000 machines in 78 countries, all working away on problems of particle physics. Another grid is being used by the Met Office to predict climate change and the EU has its own grid project, the Enabling Grids for E-Science in Europe project.
So it's just boffins that use grids then?
Not at all - it's getting a lot of attention in the business world too. Financial institutions and Wall Street staples in particular have been early adopters of the technology. Several of the major vendors involved in flogging grid - including HP, IBM and Sun - have been trying to tempt more bankers into using the technology with 'pay as you go' style offerings, the idea being that the City boys can rent a bit of extra computing power from the vendors when they need it.
As well as the number crunchers, grid has seen some interest in the retail and transport sector.
Right. All sounds a bit niche to me - when will it be mainstream?
Analysts seem to favour the 'next few years' as a likely target, with one estimate putting the grid market as being worth some $12bn by 2007 - but, like most new technologies, it'll surface first in non-mission critical applications before sceptical CIOs will pluck up the courage to get more friendly with grid.
So what's the hold-up then? If it's such a great idea, why is no one doing it?
Like most new technologies, standards are one of the main problems. And with grid intending to connect up any number of machines potentially running a huge range of software between them, middleware - and therefore standards - is crucial.
Given that standards are still being defined in various areas such as apps and data management, that more than one body, including OASIS and the Global Grid Forum, is working on defining them and that a vendor-led coalition is not ruling out the possibility of developing its own standards, some would-be grid users are waiting for the area to mature a little before jumping in.
Currently, however, the Globus Toolkit - put together by the founding fathers of grid, Dr Ian Foster, Steve Tuecke and Carl Kesselman - is the de facto standard for the technology.
So where's grid going?
Some people have speculated that one possible result could be that grid could eventually grow either to replace or enhance the internet, with spare computing power distributed around the world when it's needed, where it's needed.
It is indeed. However, while some people believe users are unlikely to share their spare capacity with people they don't know - the security implications alone are huge - others point to the illegal P2P network as a potential model. After all, music sharing started purely with some people wanting to share their record collections with others with no view to making profit.
Jo Best has been covering IT for the best part of a decade for publications including silicon.com, Guardian Government Computing and ZDNet in both London and Sydney.