Meaning of Brut, Sec, Demi-sec, Doux - difference between wines

What is the meaning of Brut, Sec, Demi-sec and Doux titles, written on wine or champagne bottles ? What are the differences between them ?

These titles indicates the sweetness of wine or champagne. They represent amount of sugar content
in grams per litre. The levels of sweetness starts from dry to medium and sweet. According to European Union terms for sparkling wine, you can find the following types of sweetness:

Brut Nature (no added sugar) - 0 to 3 grams of sugar per litre
Extra Brut - less than 6 grams of sugar per litre
Brut - less than 12 grams of sugar per litre
Extra Dry - between 12 and 17 grams of sugar per litre
Sec - between 17 and 32 grams of sugar per litre
Demi-sec - between 32 and 50 grams of sugar per litre
Doux - more than 50 grams of sugar per litre