Q. Explain traditional computer clusters?

Grid computing employs resources of a lot of separate computers linked by a network (generally internet) to resolve large-scale computation problems. SETI home project launched in mid-1990s was first well known grid computing project and it has been followed by numerous others project covering tasks like research into drugs for cancer, protein folding, mathematical problems and climate models. 

Grid computing provides a model for resolving massive computational problems by making use of unused resources (disk storage and/or CPU cycles) of huge numbers of disparate frequently desktop, computers treated as a virtual cluster embedded in a distributed telecommunications infrastructure. Grid computing concentrates on ability to support computation across administrative domains which set it apart from traditional distributed computing or traditional computer clusters.