The Restriction of Hazardous Substances is an effort to reduce the use of hazardous substances like mercury and lead in manufacturing. This is important to the field of technology as personal computers and their components have used small amounts of hazardous substances for a long time. In Europe, customs will not allow the import of products that are not RoHS compliant.
PC and technology manufacturers are finally latching onto the idea that their customers not only want low power devices for their financial benefits of lower costs for operation (included lower demand on cooling systems), but also for their benefit to the environment due to less electricity being used. PC and technology manufacturers would also be smart to promote their products as non-hazardous, as opposed to simply displaying the "RoHS badge".
Is their a computer equivalent of "organic"? :-)