There is a very distinct difference between garlic powder and garlic salt so it is therefore important for those who enjoy cooking to realize the distinction. Garlic powder is essentially dehydrated garlic cloves that have been ground into a fine powder. You will be able to find different brands of garlic powder with some being of a higher quality than others.
The truly high quality garlic powder is mostly garlic and less artificial flavorings. Keep in mind that not all garlic powder is completely pure. Many times companies use artificial ingredients in theirs, so you will definitely want to watch out for that. Although these two can be substituted for each other is most recipes, they cannot be substituted in equal amounts.