I came across this blog post about least angle regression, and at a point he says:
Find the variable $x_1$ most correlated with the residual. (Note that the variable most correlated with the residual is equivalently the one that makes the least angle with the residual, whence the name.)
Move in the direction of this variable until some other variable $x_2$ is just as correlated.
But I couldn't visualize it. By "residual" he is referring to the vectors minus the average of the vectors, am I right? What could be a geometrical interpretation of "variable correlation with the residual"? What would be a, let's say, 2D example of this interpretation?