The bus system in Paris is complex. First you need THE Book, on where the busses go and what the numbers mean.  That book is "Le petit Parisien, 3 plans par arrondissement” – found around Paris in lots of places – and even on the web in some travel shops.  It is worth getting before you head off – nice reading on the plane, so you can plot your journey around Paris , above ground.  It has the Metro lines in it too – and actually great resolution of the whole of Paris .  For each arrondissement it has a street map, a bus map and a metro map – transportation is so dense in Paris , you can not put all three on the same page.  It has the taxi stands also tucked in there with the various daily markets of Paris .  This is truly the book that helps you get around Paris , and see the city…