Ginger root is used fresh but is also available dried in powder form.
Ginger is very often used fresh. It has to be peeled, then either, chopped, sliced, minced, or grated. It is a strong flavouring agent and pairs well with many things.
In Chinese cooking, cong jiang suan, (leek, ginger and garlic) is a basic flavour combination.
In Japanese cooking, ginger is widely used in broths and marinades. Pickled young ginger (gari) is always served along side of wasabi with sushi or sashimi dishes. It is meant to act as a palate cleanser between bites.
In Indian cooking, ginger and garlic is very often used in bases for curries and chutneys.
Ginger powder is very strong and the flavour is quite different from fresh ginger. It should be used sparingly even in baked recipes where ginger is meant to be the dominant flavour such as gingerbread or gingersnaps. It really comes across as a fiery or hot taste.
Ginger can even be stored in the freezer in a pinch. It's best to peel it first. Then to use it, run it over a zester or microplane and add it right into your cooking.