Lecture notes are provided as a guide of the content of lectures for pre-reading, revision and for students who cannot attend lectures. While almost every effort is made to make the online notes as complete as possible, there is always material discussed in lectures that is not in the notes.
You should not rely on these notes only!
If you miss a lecture and you do not understand something in the notes, you should consult (in this order) other students, the tutors, or the lecturer to try to work it out.

You are expected to read these lecture notes as well as attending lectures, as vital information is contained in both.