The French, of whom I am generally no fan, have to be given credit for inventing modern European cooking. When dinner practically everywhere else in Europe meant a hunk of roasted meat (if you were rich, maybe some turnips or cabbage if you weren't) and some beer or ale, the French began getting creative with the cooking process: using herbs and spices for more than covering up the taste of rotten meat, combining food, sauces and so on. To be fair, though, I have read that much of the real credit for this belongs to cooks brought with her from Italy by Marie de Medici ( http://www.historylearningsite.co.uk/marie_de_medici.htm
) when she was married to Henri IV of France.
All of this progressed to the French classics common to American "French" restaurants up until maybe the '50's: heavy with sauces that often incorporated wine,brandy or cream, complex in preparation, frequently involving ingredients less commonly eaten in the America like duck, (famously) frogs and snails, veal and so forth. And a lot of it was formalized over the years by the French cooking schools and books written by the likes of Escoffier (see http://www.geocities.com/NapaValley/6454/escoffier.html
). But starting in the 60's, well known French chefs began devoping what they called "nouvelle cuisine" which also resembles so-called "California cuisine". Both involve use of the finest and freshest obtainable natural ingredients and cooking them simply (in France, this was revolutionary), sometimes with a sauce that is just a reduction of the cooking liquid or using a simple stock. The idea is to produce food that is a distillation of the perfect taste of the ingredients.
What may make French food a bit hard to discern from other European food is that French techniques spread so widely in Europe over the centuries after 1600. Some hallmarks of the original, though: (1) The French don't seem to make much use of tomatoes (I don't know why; and this doesn't apply to the Mediterranean coast near Italy)), (2) they rarely use "hot" flavors or peppers, (3) they use a lot of "variety meats", (4) they seem to love thyme, (5) near the coast, they get really creative with seafood.
Obviously, it's not easy to summarize a cuisine as varied and complex as the French in a few sentences and I have greatly over-simplified, summarized, etc. But hopefully, this'll help.