It says to graph the linear equation the equation is y=x-2. i just don't get it. can someone explain?

Y = 1x -1 
 
So, just follow y = mx +b
m = 1 
b = -1 
 
m is the slope so do rise       which is :  1
                                                            ---
                                    run                          1

b is the y intercept, so that is your starting point, that's where you will place your point of origin at.
Place your dot at (0, -1) then count 1 up, and 1 to the right. Place another dot there, and continue over and over till you get a nice straight line that you can draw 

:)