Oxford Comma

I often add a comma before the word 'and' at the end of a list, for example, "We sell paper, pens, and envelopes". I don't remember where I picked up that habit, but I use it most of the time to make the meaning of a sentence clear. And I didn't know it actually had a name .... until today. It's called an "Oxford comma". 

http://blog.oxforddictionaries.com/2011/06/oxford-comma/