ArcInfo is a big program with a large number of commands, most of which have many variations. You should be thinking of using this product if you are processing large amounts of data. Each of these have very distinct purposes and has a unique command set.
Arc is the basic package and is most useful for creating and processing data.
Arcedit is the graphical editing environment. It is similar to the other three parts of the package - there is a data creation, processing, editing, and display capabilities in grid. GRID provides efficient spatial-storage faclities and a modeling environment. Raster data is an effective way for storing continuous surfaces like elevation data, rainfall data, and other environmental data. As you get started, please use the online help.