Tessellation is the process of subdividing a surface into smaller polygons (shapes) for rendering. The smaller the polygons, the more accurate the appearance, but the greater the impact on performance.
Levels of Detail (LODs) are the different depths of tessellation that can be used for CAD (computer-aided design) models. Typically, LODs vary from low-fidelity (larger polygons, poor surface quality, and high rendering speed) to high-fidelity (smaller polygons, excellent surface quality, but may take time to render).
For example, the sphere in the following illustration is displayed, from left to right, with low- to high-fidelity LODs.
