What is exactly ortho effect in Reimmer-Timmer reaction?

Question

In the Reimmer-Timmer reaction cho group is added to only at ortho position not at para position , I got the answer for this as ortho effect. So what is exactly ortho effect.

Answer 1

I think that the coordination step is responsible for the ortho selectivity. The phenoxide anion has a large negative charge on the oxygen atom, so the electron-poor carbene will tend to go there and the conjugated attack will result in the ortho product.