How finance folk use it
In investing, mark to market is a commonly used method of seeing how much an asset, fund or portfolio is worth. It gives an easy way to check the value according to how much it is bought and sold for.
Is it good or bad?
When something is marked to market, its price is determined by the supply (sellers) and demand (buyers) in a market. When the supply is low and demand is high, the price goes up. When the supply is high and demand is low, the price goes down.
Seeing how much something is being sold and bought for makes it easy for you to judge its value, so you can see if your investment has gone up or down or decide to put your money in it if the asset has the potential to rise.
What it means for you
When you need to know how much an asset or other investment is worth, checking the market price is an easy way to find out. Of course, this value is not set in stone, and can change according to the supply and demand.