What is a biodegradable oil?

It is a lubricant formulated with a combination of biodegradable base oils (rapeseed or sunflower vegetable oil, synthetic ester, etc.) and special additives to reduce the environmental impact in the event of accidental spills while at the same time providing the desired lubricating properties.

Related questions:

• What to do with used oil?
• Is it good to add an extra additive to an engine?
  
• Can synthetic oil be mixed with mineral oil?