First, larger the number (ignoring any minus signs) the steeper the line.  Thus, we can use the slope to tell us something regarding just how steep a line is.

Next, if the slope is a +ve number then the line will be rising as we move from left to right.  Similarly, if the slope is a -ve number then the line will decrease as we move from left to right.

We can employ the final two parts to see what the slopes of horizontal & vertical lines will be. A horizontal line will always contain a slope of zero & a vertical line will always have an undefined slope.

Now we have to take a look at some special forms of the equation of the line.

We will begin with horizontal & vertical lines.  A horizontal line along a y-intercept of b will have the equation,

                                             y = b

Similarly, a vertical line along with an x-intercept of a will have the equation,

                                                          x =a