Bread baking lingo

Every profession has their own lingo. As I read the lessons and posts on TFL, I keep getting confused and end up trying to search for the answers and only end up with more questions.

I have just started my first ( hopefully successfull ) starter. Its only 6 days old and cant wait to use it. In the meantime I read more on bread baking and realize I need a glossary for bread baking lingo. Words that I don't understand and cant find explanations for here:

Levain, retardation are two I don't understand, unless I understand it in "other words". What is Pain au Levain?

Sorry I don't have money for books on baking bread. Is there a link someone can give me that is like a glossary of bread baking lingo?