PLA (polylactic acid) is made from biological materials such as corn starch or sugar cane, which makes it biodegradable. Like other corn or sugar-based materials, it is slowly degraded by many common bacteria. However, it will last a long time under normal conditions, so you have to, for example. don't throw it in the compost pile.
Depending on the composition it melts at 180-200 °C. PLA begins to deform at temperatures above 60 °C and is not water or chemical resistant. PLA has strong interlayer bonding, but the material itself is brittle and less elastic.
There are a wide variety of PLA blends, containing wood, bamboo (added to the plastic as fibers), metal, luminescent (phosphorescent pigment added). Other variants do not change the appearance of the material, but the properties when used in FDM 3D printing. There are variants of PLA that make it both less brittle and more heat tolerant. Some variants require curing or annealing in an oven to obtain the desired strength. However, this causes the print to shrink, which may be worth taking into account if it is a functional part where tolerances are important.
When PLA is heated, it gives off a sweet scent. Unlike ABS, it does not emit toxic fumes, so a cabinet is not needed. In general, PLA is easier to print with and requires a lower temperature than for example ABS or PETG and does not need a heatbed in order to stick to the build plate of the printer.
Easy to print with
Can be printed at high speeds
Low tendency to warp
No heatbed required
No toxic fumes
Deforms at relatively low temperatures