Microsoft Office is actually a "suite" of computer programs. It includes a word processor called Word, a spreadsheet called Excel and a presentation program called PowerPoint.
A Variety of Versions
While almost every version of Office contains those three programs, Microsoft may offer up to nine "flavors," depending on your budget and needs.
Scalability
These flavors also vary substantially in price.
Volume Licensing
With volume licensing, Microsoft can sell you a large batch of "product keys" for Office. You can use the same physical copy of Office to install on these computers, while allotting each install one of those product keys.
Separating Components
Most of the individual applications in the Microsoft Office suite can be purchased separately. Buying a suite costs less than buying multiple components separately.