Difference between the book value and the market equity value!

"Specifically, the book value of assets is the price paid for the assets, reduced by depreciation over time. Likewise, the book value of liabilities reflects  the  liabilities  when  they  were  first  obtained.  The  difference between the book value and the market equity value is that book value is often based on a historical cost, and the latter is the “up-to-date” assessment of the value of the assets minus liabilities."

Difference between the book value and the market equity value!