Grid computing has been around for over 12 years now and its advantages are many. Grid computing can be defined in many ways but for these discussions let's simply call it a way to execute compute jobs (e.g. perl scripts, database queries, etc.) across a distributed set of resources instead of one central resource. In the past most computing was done in silos or large SMP like boxes. Even today you'll still see companies perform calculations on large SMP boxes (e.g. E10K's, HP Superdomes).

Virtualization seems to be the buzz word all in IT are using these days. It can mean a bunch of different things depending on who you talk to. Refer to Wikipedia for many of the latest definitions. For our discussion let's define it as a technique for hiding the physical characteristics of computing resources in a way in which other systems, applications, or end users interact with those resources.