There are a lot of aids for this lesson; not that it's terribly confusing, but it's a bit better to play with some simulations to really let it sink in. Firstly, there are two videos below: mine and the author's. Secondly, Lesson Two of the TUTORIAL should be done now. Thirdly, here is an excellent SCREENCAST on types of waves. Finally, here is an INTERACTIVE FIGURE that links frequency and wavelength together.
Source: Hewitt, P. G. (2015). Conceptual Physics (12th ed.). Boston, MA: Pearson.
Source: HEWITT, P. G. (2015). CONCEPTUAL PHYSICS (12TH ED.). BOSTON, MA: PEARSON.