Can Someone Explain Mintmarks From France And Netherlands?

The short answer to your question is "yes". The longer answer is more complicated than that.

They're called "privy marks", and they serve much the same purpose as mintmarks. They descend from the mediaeval practice of each mint official having his own personal mark or symbol that he used on all the coins he was responsible for; if he went to another mint, or even another country, he would probably take his mark with him.

In early modern France (1600's and 1700's) up to four marks could appear on a coin: the mintmark letter, the mint director's mark, the mark of the engraver that actually made the particular die being used and the mark of the Engraver-General (the chief engraver of the country). Mint engraver's marks were no longer used by the time of the revolution and in 1880, the privy mark system was further simplified: the cornucopia privy mark now represents the office of the Mint Director-Administrator, rather than the actual person that holds that office; the only marks to appear on modern French coins are the cornucopia and the Chief Engraver's marks. You'll also see these marks on the coins of the French colonies.

Much the same story happened in the Netherlands, except there the mints acquired permanent mintmarks, while the Mintmasters personal marks changed. Today, the privy mark for the Utrecht mint is the caduceus, and this never changes; it effectively is a proper mintmark, though it's pictorial rather than alphabetic. The other privy mark on Dutch coins is the personal mark of whoever the Mintmaster was at the time the coin was made.

The French mintmark-letter system isn't as simple and commonsense as the American "D for Denver". Mints were ranked in order of age and/or prominence. A was Paris, B was Rouen, and so forth. In pre-revolutionary France, they had so many little tiny mints that they actually ran out of letters, and had to start using other symbols. The "B" mintmark you see on some early to mid 20th century coins was the last remnant of this system; look at the mintmark closely and you'll see it's actually a "doubled B"; that mark stands for Strasbourg.

The Germans had (and to an extent still have) a parallel system, where A = Berlin etc.

This old thread discusses French mints of the 19th and 20th century in more detail. I actually found the thread by Googling "French mintmarks" - it was the #1 hit.