There are several types of mint, but spearmint, also known as common mint, is the most commonly available. It's an idea to buy bunches of mint from local Asian shops where it's sold for a fraction of supermarket prices. The flavour is so much more intense and fresher too.
Garden centres offer a range of fruit-flavoured mints, including apple mint and pineapple mint. Other varieties include peppermint, used in confectionary. There's even a chocolate mint, which, as its name suggests, has an after-dinner mint chocolate taste.
The best way to keep mint is to plunge bunches, stem down, in a jam jar, and cover the leaves with a loose-fitting plastic bag. It's best stored this way in the fridge and will stay fresh for 3-4 days.
Dried mint is often used in Middle Eastern and Asian dishes, and is particularly tasteful when sprinkled over flatbreads. It does, however, become musty within a few weeks of drying, so use it as soon as possible, and freeze any remainder in an airtight plastic bag.