1) Expert 2) French word used in English 3) Versed 
• Expert; skillful; well instructed.
Au` fait' (ō` fa'). [ French Lit., to the deed, act, or point. Fait is from Latin factum . See Fact .] Expert; skillful; well instructed. 
Another one of those French expressions that have slipped into the English language. This one means to be familiar with something. I'd say at the end of reading all this you'd be au fait with the differences between American and English!
having experience or practical knowledge of a thing; expert; versed.