Splines and particularly cubic splines are very popular models for interpolation. Historically, a ``spline'' was a common drafting tool, a flexible rod, that was used to help draw smooth curves connecting widely spaced points. The cubic spline curve accomplishes the same result for an interpolation problem. In these notes we describe cubic splines and discuss their use in interpolation and curve fitting. Many texts give the algorithms for determining the spline coefficients, so we do not do that here.