What do we mean by $CP^2$ with reverse orientation?

307 Views Asked by At

$CP^2$ and $\bar{CP^2}$ are not diffeomorphic since they have non-isomorphic intersection forms. so why do we call the latter $CP^2$ with reverse orientation? it seems like we are not just reversing a given orentation on $CP^2$ to get $\bar {CP^2}$.