Pre-calculus can mean a few different things, depending on where it is studied. Typically though pre-calculus is a study of all the skills required to do differential, integral, vector, and advanced calculus. Pre-calculus is usually studied in high school, but many university courses go through the material as review. There are two major chapters to pre-calculus studies; Function and Limits;
The functions chapter covers all of the essential function properties from previous algebra courses. Functions can be represented in many different ways, this includes verbally, visually, algebraically, and numerically. In calculus we typically express them algebraically or numerically. The formal definition of a function says that ‘a function assigns each element in set 1 to an element in set 2’. This basically means that one variable in a function cannot be mapped to more than one values. In pre calculus the major functions we examine are; Linear, polynomials, power, exponential, logarithmic, and trigonometric. There are so many properties to remember for all of these types of functions. They will come up often in calculus studies, so there are plenty of chances to put them to use.
Limits are hard to explain in simple terms. Roughly speaking a limit is the value of a function as the independent variable approaches a certain point. But this is not necessarily the same as evaluating the function at a specified point (though in many cases it is the same). A limit may or may not exist, this depends really depends if the function goes to the same value from both sides of the graph. Limits are an essential part of calculus and are used to form the definition of the derivative. Limits are also used to determine the behavior of a function at discontinuities and infinite points.
Learn these concepts well before starting real calculus studies, a good foundation is extremely important.