What does it mean? It looks like something to turn nouns into adjectives, but so far I've only seen it in things that could have been possessive phrase. Is there a difference between -ин and using the ordinary genitive case?
Semantically I do not see any difference. The suffix
-ин is used to express posessiveness.
кошкин дом = дом кошки мамин дом = дом мамы
Grammatically you can't add more attributes to cat or mother because they've become an attribute themselves.
дом моей мамы = ? дом серой кошки = ?
Also you can't form possessive adjectives that way freely. There are many exceptions and other ways to express possessiveness:
Петька - петькин Катька - катькин (and other names formed like this apply for this rule) Нина - нинин лиса - лисий заяц - заячий
So if you have nothing else to add about
mother, go ahead and use