Linear functions are probably the most familiar functions. They are just straight lines. The standard mantra in American education is to express the formula for a line as y = mx + b. You may know this formula, but do you know what it means?
Going one step further, you probably recall that m represents the "slope" of the line and b is called the "y-intercept."
When you move from the abstraction of a generalized line with some "slope" and "y-intercept" to the applications of a particular formula, the connection sometimes gets lost. And sometimes even the simple idea of a "linear function" becomes more complex.