An orientation of a link is a choice of direction to travel around each of the components of a link.

An oriented link is a link together with an orientation. We notate orientations on Knot diagrams by drawing arrows.

Equivalence of links and Reidemeister theorem extend for oriented links.

See here and here

In a diagram of an oriented link, every crossing can be given a sign. See here.

Reverse link

Linking number