Marking to marking: setting the derivative (or any asset but mostly used to discribe futures) value to Zero, that is if you have any gain you take it or any lose you pay it, so if you want to sell your position then its value is Zero. In case of Assets, which mostly balance sheet long term assets, you update or revalue the asset to the fair market value.
Liquidity risk: basically the asset not liquid , meaning its fair value (market value) is hard to get. Or the time needed to sell it takes long time, again due to the uncertainity of the price. usually this risk priced by having a discount on it (you can think of it as a premium yeild for the risk of not being able to liquidiate it fast, due to the uncertainity about the equilibrium point between the supply and demand). Like the house maybe they are large in volume, but with in the same area same characteristic of the house, they are small in trading volume.
This is my understanding of these too concept. I hope I covered every aspect and names used to describe each