French people often have a lavish family meal at Christmas.
Starters could be for example oysters, shellfish or foie gras (may also be cooked into a main dish), or even escargots (snails in garlic butter) for those who like. The main course could be a nice piece of roastbeef, a goose, game meat, or a fine piece of red meat. It is very frequent that the menu will try to include something unusual, either expensive or original. The side serving would be greens and / or fruits, but nothing as ordinary as French fries or rice.
Adults could drink water, fine wine and Champagne , kids would have soft drinks or fruit juice.
Dessert would likely be a nice pastry, like the traditional "bûche de Noël", a log-shaped Christmas cake, or a Bavarois (a light fruit mousse).
The party and the meal itself are called "le réveillon" (the same name is used for New Year's eve party).
Joyeux Noël!
French people eat a variety of foods on Christmas. Among then are: oysters, smoked salmon, chapon (roasted chicken), dinde aux marrons (chestnut-stuffed turkey) and gnzelropf (goose).
Among deserts served is berauwecka (dried-fruit cake).
In the French region of Provence, thirteen desserts are served. They represent Jesus and the 12 apostles. Traditionally, the desserts are set out on Christmas Eve and remain on the table until December 27. The desserts are:
France has many traditional foods associated with Christmas. La Gallett Desoirs - Epiphany cake - is a family dessert. It is a rich pastry filled with an almond flavored custard called frangipane. A small porcelain figure is baked into the cake. The youngest child in the family hides under the table and calls out who gets which piece. Whoever gets it is named King or Queen for the day and gets to wear a golden paper crown.
They eat a buche de Noël, or yule log.
A buche de Noel is a a cake made to look like a log cut and ready for the fire. It's baked in a jelly roll pan (long flat pan with a lip), a filling is spread on top, and the cake is rolled, jelly roll style. One end is cut off and added to the top as a sawn off "branch" and the cake is iced to look like bark. Meringue or marzipan mushrooms and possibly berries or other decorations, including powdered sugar "snow," may complete the picture. It's a specialty widely available at bakeries (patisseries) if one does not want to make their own. This is the traditional Christmas dessert in France.
I believe they enjoy the chocolate log!
Vast quantities of oysters are eaten raw, washed down by white wine; this is often by the adults on Christmas Eve after the children are in bed.
Usually, for Christmas and the new year eve, most of the french drink a cup of champagne, often at the end of dinner.
Hors d'oeuvres
Because it's their Christmas.
The primary Christmas decoration in France is the Christmas tree (or, in French, sapin de noel).
French Christians celebrate Christmas. French Jews celebrate Hanukkah.
In France, just like in America, if you are catholic then you do. 
There are no 'Christmas clothes' in France. People do just wear their regular winter clothing.
They eat crepes and other french food
French is the language of French people, who are the ones living in France.
Very few families in France are saying grace before eating. They don't do it much more at Christmas.
la France
People in France celebrate CHRISTMAS on December 6th
"la République Française", short form: la France
No one HAS to celebrate Christmas. Most French do.
People who live in France are know as French.