Type is defined in the Combinatorica`context and is an option for many Combinatorica functions that transform graphs. Depending on the functions it is being used in, it can take on values such as Directed, Undirected, Simple, All etc. For the function ConnectionList, InterpolationCoefficients and for Interpolation, Method -> "ObtuseAngle" in the Obtuse package, the values Directed and Undirected are implemented, with Directed as default.