This German "postkarte" was mailed from La Chaux-de-Fonds, Switzerland (Helvetia) to Somme, France. If I'm reading the franking correctly, it was mailed in 1900, which would concur with the undivided back. Most European countries did not allow postcards with message space verso until 1904 or later.
The illustration is a romantic scene in blues and pinks of a couple in 18th century dress. The quality is typical German lithography which set the enviable standard. The gentleman wears a tricorne in blue which matches his jacket and the umbrella he carries. Notice how high up his leggings go. The woman is draped, beribboned and ruffled to the max. And, oh, such a coy gesture with her hand close to her lips to hide a feminine chuckle.
A piece of trivia for you. The sender crossed out "postkarte" and wrote "imprimé." Imprimé was the early version of Twitter:) If you could say something under a certain word count (I believe it was 5 words or less), the postage rate was discounted. So, some writers would only put their initials or name on front. This sender left all that white space blank on front. Perhaps Mademoiselle Andrée had a secret admirer!
Size: about 5.5 by 3.5 inches. Corner tips show wear but considering the light background and its age, this card is in almost mint condition in my opinion.