Embroidered silk postcards like this were popular around the time of World War I. “Christmas 1921” is written on the back of this card. Heureux Noel means Happy Christmas in French.
The embroidery on this type of card was machine made. Designs were embroidered on a thin cloth, usually organdy or a silk/cotton mix. Individual embroidered panels were cut from a sheet with multiple embroideries and were mounted on a postcard backing. An embossed frame was then glued on to finish the card.
Reference:Embroidered Silk Postcards