An explicit cost is something with a price tag that you pay. The explicit cost of buying a Chevy is the $10K that you spend on it. An implicit cost is usually an opportunity cost. You don't actually pay it, but it factors into your decisions. The implicit cost of buying the Chevy is whatever else you might have done if you didn't buy it. If you would have used the $10 to buy a Mazda, then they Mazda is the opportunity cost. The explicit cost of attending college is the tuition, books, etc. The implicit cost of attending college is the lost wages from crappy jobs that you would be working at if you weren't in college. Normal profit is the profit that you could be making doing something else. So, it's an implicit cost. If the normal profit is high enough, you shouldn't be doing what your doing even if the accounting profit is positive. Accountants might disagree, but they're wrong. Economic profit is an implicit cost of production because you could be using your capital to do something else. But economic profit is not an explicit cost of production because you don't pay it or lose it