The GRID computing is a form of distributed computing that involves coordinating and sharing computing, application, data, storage, or network resources across dynamic and geographically dispersed organizations. Grid technologies promise to change the way organizations tackle complex computational problems .
Computational grid can be described by analogy with electrical power grid around year 1910 when every electrified building required its own expensive generator. There was no chance to use larger capacity then that of the single single generator and total capacity of all generators were used ineffectively. The real utilization of electricity begun after connecting of power stations, distribution network, and consumers .
Similarly, todays organizations manage their own expensive computational capacities which can not be shared. Computational grid can enable effective sharing of computational resorces.It is beyond the scope of this brief descrition to discuss in detail the GRID infrastructures established worlwide.
PECS-GRID project plans utilize the European Space Agency (ESA) Grid on-Demand Services and Infrastructure (GODIS) for Earth Observation Applications  and pan-European Enabling Grids for E-sciencE (EGEE) infrastructure .
|||Foster, I., Kesselman, C.: The Grid: Blueprint for a New Computing Infrastructure, Morgan-Kaufman, 1999.|