Paris Travel Guide - HTML5

 TER : The regional trains ( Train Express Régionale ); cheapest tickets, though prices are variable on the time of day of departure (and the day of departure as well). TER are slower, stopping at almost all stations.  Intercités : A bundling of the former Intercités , Téoz , and Lunéa train categories. There are two kinds: the regular trains, which are priced the same as the TER and the trains you'll find yourself on if you have a Eurail or InterRail pass and don't want to pay extra for reservations, and the trains à réservation obligatoire , which require a reservation and are priced differently from the regular Intercités trains.