Grain drying is when farmers take the wet grains they get from their crops like corn, wheat, and rice and make them dry so they can store them for a long time without going bad. It's like when you take a wet towel that you used after a shower and you hang it on a hook to dry it out so you can use it again without it getting stinky and moldy.
The farmers use a machine called a grain dryer that blows hot air on the wet grains to evaporate the moisture. It's like when your mom blows hot air from the hairdryer on your hair to dry it after you take a bath. The grain dryer has a big drum that holds the wet grains and a heater that warms up the air before it blows it on the grains. The drum spins around so that all the grains get dry on all sides.
When the grains are dry enough, the farmers store them in big bags or silos until they need them. Silos are like big vertical tubes that can hold lots of grain. It's like when you store your toys in a toy box or on a shelf so that you can play with them anytime you want.
Grain drying is important because wet grains can get moldy and rotten if they are not dried out. You wouldn't want to eat moldy bread or cereal, would you? So, grain drying helps farmers keep their crops safe and healthy for you to eat.