One of the reasons that the DataGrid control deserves a chapter by itself is that it is probably the single most useful way to give the users of your application access to data that is in a database. The very fact that "tables" - actually the same thing as a grid or a spreadsheet - have turned out to be the most useful way to organize data in a database makes a "grid" the most useful way to present that same data again. (Back in the sixties, a hierarchy - the same way files or VB.NET Solutions are organized - was the leading way to organize databases and IBM's IMS database was the leading product. But when "relational databases" took over, all that changed.)
Programming with DataGrid also the best way to 'harden in' the information presented about databases in the previous chapter with real examples and more industry information. Since most of this lesson is based on extending the information that is in chapter 20, please read the chapter and, most important: program the examples before reading the rest of this lesson.