A FDM 3D printing plastic is malleable when heated through a print head extruder. PLA is derived from renewable materials and is biodegradable which makes it a perfect cost effective material for quick prototypes that can be recycled.
Other processes like the HP’s MJF (Multijet Fusion) or Formlabs’ SLA (Stereolithography) use plastic materials in a powder or resin form which is then formed using infrared lamps and fusing agents (MJF) or high-powered lasers (SLA).
The beauty of additive manufacturing is the ease of access to materials. Ultimaker, for example have an open access marketplace,meaning that many different material manufacturers are able to supply their materials and the setting for the printer is automatically obtained in Ultimaker’s software Cura.