Positively oriented

Traversed counterclockwise, so the region a closed contour encloses stays on the left of the direction of travel.

A simple closed contour is positively oriented if it is traced counterclockwise -- equivalently, if walking along it in its direction of travel keeps the region it encloses on your left at every point. The opposite traversal, clockwise, is negatively oriented. This convention fixes the sign of a contour integral around a closed contour, which is why Cauchy's theorem and the residue theorem are always stated for a definite orientation.

Examples

$z(t)=e^{it}$ , $0\le t\le 2\pi$ , traces the unit circle positively oriented; $z(t)=e^{-it}$ traces the same circle negatively oriented.
Reversing a positively oriented contour's direction of travel negates the value of any contour integral taken around it.