Polylactic acid [PLA] is a thermoplastic commonly used in 3D printing. It has low printing temperatures and relatively good strength while sacrificing rigidity and being fairly brittle. PLA is only suitable for low temperature applications because the glass transition temperature is between 60 and 65°C.

I primarily use PLA for quick prototypes because it is cheap, prints well at high extrusion volumes, and has a wide variety of colors.