What is the molarity of 648.72 mL of solution that contains 1.33 moles of silver nitrate (Molar mass = 169.87)?

He is using filtration technique

It's a technique which is used for separation of solids and fluids by putting them through a medium which allow only fluid to pass through, leaving the solids (in this case the soil) alone.

The fluid that passed is called the filtrate