Garlic Powder
Garlic powder isn't a true substitute for fresh garlic - nothing could be - but it does have its advantages. It usually lasts for a long while and a little goes a long way when cooking, so some people buy it as an alternative to minced garlic for keeping in the kitchen store cupboard.
What Is Garlic Powder?
In theory garlic powder is very simple: it's just dehydrated garlic cloves that have been ground to a powder. Some of the high quality brands you can buy are just that, pure garlic.
Not all of the brands on the market are pure garlic. Sometimes artificial ingredients are added to "improve" the colour or flavour. As always, it's worth checking the ingredients before you buy.