Let me first give you an overview of the coordinate plane. The coordinate plane has an x-axis that runs horizontally left to right and a y-axis that runs vertically up and down. The axes intersect at a right angle at the origin, which is (0, 0). If you have a point, say (2, 5), then the point is located two steps to the right of the origin and five steps up. Remember to always go left and right first before going up and down. This is because the y-coordinate depends on the x-coordinate.
Sometimes the y-coordinate is called f(x), which is the function value at a given x-value. Again, this is because f(x) depends on the x-value.
The numerical value of f(4) is how ever many steps up or down the graph is (the graph is a visual representation of f(x) points). At x = 4, the graph is at 1, so f(4) = 1.
