AutoCAD Civil 3D supports several types of surfaces:
TIN surfaces. Formed by triangulating an arbitrary set of points. For more information, see Creating a TIN Surface.
Grid surfaces. Formed from points that lie on a regular grid (for example, Digital Elevation Models (DEMs)). For more information, see Creating a Grid Surface.
TIN volume surfaces. A composite surface created from a combination of points in a top (comparison) and base surface, also known as a differential surface. For more information, see Creating a TIN Volume Surface.
Grid volume surfaces. A differential surface based on user-specified top and bottom surfaces with points on a user-specified grid. For more information, see Creating a Grid Volume Surface.
Corridor surfaces. A corridor surface is a surface created using data extracted from an underlying corridor model. For more information, see Creating and Editing Corridor Surfaces.