The material in Section 2.2 of the book on scanning presumes some knowlege of finite automata. The prequisites of this course do not cover that, though you may have taken a class (algorithms or models of computation) which did. We will go over FA in class, and the following resources may be helpful as well:
Please do not hesitate to visit me at office hours, espcially if this material is new to you! Also, the CD that comes with PLP has a brief introduction to FA (CD section 2.4.1). The links above may be more helpful though.