PHA (Polyhydroxyalkanoate) filament is a biodegradable type of plastic used in 3D printing, made through the fermentation of plant sugars by bacteria. It's known for being environmentally friendly, making it a great choice for applications that require biodegradability, such as disposable items and medical implants. PHA is more flexible and has better UV resistance compared to PLA, making it suitable for outdoor use. It also degrades more easily in natural environments than ABS, offering a greener alternative without the need for special conditions or toxic chemicals for breakdown.