Welcome, finings are usually used towards the end of fermentation to clear beers, wines and ciders. Once a brew has finished the primary fermentation finings can be added to settle the suspended yeast to the bottom of the vessel and clear the brew, this is common with wines as it then leaves the wine clear for bottling, it is less common with beers as you need some suspended yeast left to create the secondary fermentation in the bottles/barrel and carbonate the brew. Most beer and lager ingredients do not include a finings and the brew will settle naturally and clear, using finings can increase carbonation times, more details are here if of any interest:
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