"En Plein Air" is a French phrase which means "in the open air".  These paintings were completed outside at the locations depicted.  Most were completed in one session.  The result is hopefully a painting that is more true to the actual scene than can be accomplished using only photographic reference and memory.   These quick studies capture the color and light of the moment.  In many cases they are used as a reference for more formal studies completed in a studio.  Because of their spontaneity and liveliness, many consider them to be complete works all on their own.