# Correlation of errors between regression equations?

I know that one can use Seemingly Unrelated Regressions when for an observation i, there are two equations whose errors are connected.

What is the intuition here among errors of difference equations have some sort of relationship? In the SUR case, is it simply because unobservable factors (say, for example, general attitude towards spending money) that explain things like consumption for food in observation 1 will also explain consumption for clothing, for the same observation 1?

Also, how does one call correlation between errors in this case? I understand it's not serial correlation, nor spatial correlation in this case.