Sauces are, of course, a crucial element of French cuisine, and the French cook can recreate the canon of sauces from a limited set of techniques and ingredients. Here's a quick run down of some very basic sauce-stuff:

Béarnaise:

A relative of hollandaise, béarnaise is a reduction of vinegar, tarragon and shallots that is finished with egg yolks and butter.

Béchamel:

Add milk or cream to a white roux and voila! it becomes a béchamel.

Hollandaise:

A hollandaise uses butter and egg-yolk as its liasons. It is served hot with vegetables, fish and eggs -- like on eggs benedict.

Liaison:

A liaison, or binding agent, is the base of any French sauce. Sometimes called a binder, egg yolks, butter, flour, and puréed vegetables, are all liaisons.

Reduction:

A reduction is the mixture that results from rapidly boiling a liquid (like stock, wine, or a sauce)and causing evaporation -- "reducing" the sauce. The reduction is thicker and has a more intense flavor than the original liquid.

Rémoulade:

This classic sauce mixes mayonnaise, mustard, capers, chopped gherkins, herbs, and anchovies.

Roux:

Roux, a combination of flour and a fat, often butter, is perhaps the best known liaison. A roux can be white, blond, or brown, depending on ingredients and cooking time.

Velouté:

Mix a white roux with white stock (light chicken or veal stock) and it becomes a velouté.