The airlock is a small device that allows the carbon dioxide produced in fermentation to escape, while preventing air from outside the fermentation chamber from getting in. Apparently, this enhances the effectiveness of the fermentation process, assuming that your fermenter has a sealable lid. Airlocks work by using a small amount of water in a u-shaped tubing bend to allow the carbon dioxide to escape as bubbles under a small amount of pressure.

As a newbie myself who has done 3 weeks of exhaustive research on fermenting and distillation, I don't know anything about stirring mash once per day. I know that you would stir the mixture of water, sugar, cracked corn, malted ground barley,(and possibly some alpha amylase), in a pot at between 153 to 158 degrees F for over an hour while frequently stirring. After that, you would place the mixture into the fermenter and let it cool to about 90 degrees F, stir in the yeast, and leave it alone for anywhere between 5 to 8 days. My information came from a wide variety of sources which required comparison, evaluation, and condensation to separate the fact from the fiction. It is very difficult to get a straight, consistent answer off the internet.