What is the difference between ils and elles?
Is if for a group of men and a group of women? What if it is a combined group?
"Elles" - women, "ils" - men. If there are both men and women, you use "ils".
Note that in French all the nouns have genders. "La voiture" (the car) is feminine, so "they" for "cars" would be "elles". And so on.
So would it work the same for other things? Like a group of male and female dogs would be chiens? As in all combined groups are automatically masculine?
For a combined group of any things or people you would use "ils" if you need a pronoun. A group dogs can be just "chiens" if it does not matter if they are feminine or masculine, but if it does matter, you would say, like, "les chiens et les chiennes".