This course builds on the algebra, trigonometry, and pre-Calculus sequence. You should be familiar with functions (domain, range, vertical line test, horizontal line test, etc.) in general and have some comfort working with trigonometric, logarithmic, and exponential functions. Given a function and two points in its domain, you should be able to find the corresponding secant line on its graph. Given a (relatively simple) function representing the motion of an object, you should be able to find the average velocity of that object over a given time interval.
If you have registered for the course and want to brush up before the semester starts, there are a couple things to try.
If you already have our book, then Chapter 1 is a good review. Here are some questions from the Chapter review.
We have a Precalculus textbook here.