If you're saying that you're having a hard time understanding the y-intercept, I can help you with that.
If you can picture a typical graph (Cartesian plane) with an x-axis and a y-axis and the origin in the middle you'll be able to understand this easier.
The y-axis is the thicker line that runs vertically up and down the center of the graph. When you try to find the y-intercept, you're looking for the point where the line/function that you are studying hits/touches/intercepts with that y-axis line.
One important thing that you can note when you're trying to find the y-intercept is that you know that it is somewhere on that up/down y-axis. That then means that you won't have to go left or right from the origin to find the y-intercept; only up or down (or at the origin itself). Since you know you won't be moving horizontally at all, you know that the x coordinate of the y-intercept will be 0. So the point of the y-intercept will be in the form (0,y).
To figure out what that value of y is, use what you already know and the equation you have. Your equation is y = x - 2. You know that x is 0, so plug 0 in for x in the equation. This makes your equation y = 0 - 2, which is equal to y = -2. That means that the y coordinate is negative two.
So for that equation, the point of the y-intercept is (0,-2)
