For a regular space curve $\gamma$ at each point one can define a triple of vetors: a tangent vector $\tau$ (tangent to $\gamma$), a normal vector $\nu$, and a binormal vector $\beta$.

These vectors together make an orthonormal basis that is called a Frenet (orthogonal) moving frame.

The model shows a Frenet moving frame along a helix-like curve. A helix is the only spatial curve with constant curvature and torsion.