I doubt most folks understand what "Mark to Market" means to them. But then again, most folks don't really understand much of anything, do they.
In finance and accounting, mark to market is the act of assigning a value to a position held in a financial instrument based on the current market price for that instrument or similar instruments. For example, the final value of a futures contract that expires in 9 months will not be known until it expires. If it is marked to market, for accounting purposes it is assigned the value that it would fetch in the open market currently.