PLA is an abbreviation of Polylactic Acid. It is different than most thermoplastic polymers in that it is derived from renewable plant-based resources like corn starch or sugar cane. CPLA is Crystalised PLA, and has simply been made to be more rigid so that PLA can be used for more purposes (like a coffee cup lid).
Petroleum-based plastics, by contrast, are derived from the distillation and polymerization of nonrenewable mineral oil reserves. Polylactic Acid is biodegradable and has characteristics similar to polypropylene (PP) and polyethylene (PE). It can be produced from existing manufacturing equipment (those designed and originally used for petrochemical industry plastics). This makes it relatively cost-efficient to produce.
Accordingly, PLA has the second largest production volume of any bioplastic (the most common typically cited as thermoplastic starch). Plastics that are derived from organic matter (e.g. PLA) are known as “bioplastics.”