Simple interest works in your favor when you borrow money, while compound interest is better for you as an investor.

CNBC Select defines compound interest, how it works and ways to take advantage of it if you're looking for a new credit card or somewhere to stash your cash.

For many 30-year-olds, the dream of becoming a millionaire might seem far-fetched, but with strategic planning and disciplined investing, it is attainable. By understanding the principles of compound ...