Business value is the value that a business creates through sales or services. So essentially, income - expenses + goodwill.

Market Value is the price of the stock x outstanding shares. The problem lies in that a stock price does not necessarily correlate to how well the business is doing or not doing. And the stock price can be manipulated by the Business (cut expenses to the bone to make the QTR/YR look fantastic) or by rumors or by loud mouths on TV who have a vested interest in the company, so they talk it up. Or by a tweet by the CEO claiming they'll be able to do something which everyone knows they won't, but hell, why not buy the shares.