A false bottom is a perforated or slotted screen on the bottom of a mash tun or lauter tun that restricts grains from being collected with the wort when it is drawn from the mash in preparation for the boil. There are a variety of false bottoms available for home brewing.
Turbidity is haziness or cloudiness in beer or wort. It is caused by the suspension of particulate matter in the fluid. In order to remove the turbidity of wort in the mash or lauter tun, it is recommended that you recirculate the wort over the grain bed, which will act as a particle filter. Recirculation is a great method of clearing the wort prior to sending it to the boil kettle.
A lauter tun is a brewing vessel used by large scale breweries. After the mash has completed, the grains are transferred to the lauter tun where the converted sugars can be thoroughly extracted from the grains. The lauter tun has rotating arms with cutting blades that rake the mashed grains. Hot water is sprayed upon the grains to flush the sugar though a false bottom at the base of the lauter tun.