Although ą looks like an a with a tail it has nothing to do with an a sound - it is actually a nasal o. Polish is the only Slavic language which still has nasal vowels (apart from Kashubian which is often considered as a dialect only). The tricky thing about ą and ę (nasal e) is that most of the time they represent two sounds - the exact pronunciation depends on the letter which follows it. Here are the rules: