Limits
Limits are a part of calculus. They are used to approximate the value that a function approaches as it approaches.
In order to find limits, you have to check from both the left side (-, smaller value -> larger value) and the right side (+, larger -> smaller). As expected of functions, the x value will be your input (the values used to find the limit), and the y value will be your output (the value the x values are approaching).