You can't go through algebra without learning about functions. This tutorial shows you a great approach to thinking about functions! Learn the definition of a function and see the different ways functions can be represented. Take a look!
If you graph a linear function, you get a line. If you graph a quadratic function, you get something called a parabola. A parabola tends to look like a smile or a frown, depending on the function. Check out this tutorial and learn about parabolas!
Dealing with graphs of quadratic equations? You should know about the parent function graph first! All graphs of quadratic equations start off looking like this before their transformed. Check it out!