Functions are mathematical building blocks for designing machines, predicting natural disasters, curing diseases, understanding world economies and for keeping airplanes in the air. Functions can take input from many variables, but always give the same output, unique to that function. I would say walking as an example of a function from my daily life. Since I walk to school, I take at least 5000 steps every day. I burn calories as I walk. We can construct a function of calories burned for each step. For example, if f(x)=2x^2 is my calorie-step function, this means that if I take one step, I will give 2 calories, and if I take 2 steps, I will give 8 calories. It is an increasing graph as the calories I give increase with each step I take. When we look at my function, we can also see that it is an even function. With this function we can also calculate the average rate of change and instantaneous rate of change as well.