what are these stains?

i'm trying to get rid of them but i don't see any options to do so. there's multiple of them in my house and they look quite ugly

https://preview.redd.it/f3uvcjb4qbhh1.png?width=307&format=png&auto=webp&s=51ed3685b52fb4f98f5eba6b4644243ac1beaa81

https://preview.redd.it/7ysc6az5qbhh1.png?width=492&format=png&auto=webp&s=6227147b059103da1a8a970426e62a6e77941122