Substitution is the lowly chocolate kiss. It works just fine - but it's pretty basic - not anything special. In this model technology is used to do the very same thing that you were doing without tech. The task stays the same.
Augmentation moves one step up the ladder so the chocolate kiss becomes a bit yummier with caramel filling. In this model task remains the same but technology is used to add a bit more, the tech takes the process to a new level
Modification adds peanuts to the mix of caramel and chocolate. In this level the task begins to change. The use of a tech tool moves the process to a different place - allowing more options than existed without the tech.
Redefinition changes everything - our candy is not just a candy but a yummy chocolate ooey gooey dessert. Technology takes the task to a completely different place - redefining and reshaping the very activity.