FDM (Fused Deposition Modeling) Is the 3D Printing technology most people are familiar with. It starts with a string of solid material called filament. This filament is fed into a heated nozzle where it melts and is extruded in a predetermined path, layer by layer to build the 3D Model.
This is the most affordable type of 3D Printing you can find, with the highest variety of materials. PLA, and ABS are the most common types and are available in a wide variety of colors.
FDM is great for quick, low cost prototypes for a wide variety of applications.