We’ve already talked about genders in French… there is more 
There are some words that are spelled exactly the same way… but they change meaning if they are used as masculine or feminine.
How come ?
I explain :
MOULE – “un moule“, masculine, is a form, a mould, a tin, a pan… “une moule“, feminine, is a mussel.
LIVRE – “un livre“, masculine, is a book… “une livre“, feminine, is a pound.
MOUSSE – “un mousse“, masculine, is an apprentice sailor… “une mousse“, feminine, is a foam. In fact we wouldn’t talk about “une mousse“ but more about “la mousse“ for “some” foam. “Une mousse“, feminine, is also a casual name for a beer … very visual !
PAGE – “un page”, masculine, is a page in the Middle Ages… and “une page”, feminine, is one side of a sheet of paper in a book… funny, you have the same two pages in English… but you don’t have to bother with the gender, right ?
There are many other words that are either/or… with different meanings. This was just a sample.