This slide hints at what comes a little later in this lecture. The function $E(u,v)$ represents an approximation of the error function defined on this slide. In short, the error function computes the difference between two patches within an image, where the displacement between these two patches is given by $(u,v)$ (described in terms of pixels). So when $(u,v) = (0,0)$, the displacement is zero and the difference between two patches is also zero (since we're comparing the patch with itself). As $(u,v)$ gets larger, the displacement is larger and you expect the difference between two patches to get larger as a result.
What are u and v?
This slide hints at what comes a little later in this lecture. The function $E(u,v)$ represents an approximation of the error function defined on this slide. In short, the error function computes the difference between two patches within an image, where the displacement between these two patches is given by $(u,v)$ (described in terms of pixels). So when $(u,v) = (0,0)$, the displacement is zero and the difference between two patches is also zero (since we're comparing the patch with itself). As $(u,v)$ gets larger, the displacement is larger and you expect the difference between two patches to get larger as a result.
Thanks for the answer!