The term carrier oil is used frequently, but what does it mean?

Many recipes call for polysorbate to solubilise oil into water.  Confusingly, there is more than one polysorbate.  When should polysorbate 20 be used and when do you call upon polysorbate 80?  This article will help sort out the confusion

Who would have thought Bicarbonate of Soda could have so many uses?