Okay, imagine you have a special kind of stove that is called an air-tight stove. This stove is like a special box that you put wood or other fuel inside to make a fire. The stove has a special door that you close really tightly to keep the fire inside and not let any air escape.
When you light a fire inside the air-tight stove, the heat from the flames warms up the inside of the stove. As the stove heats up, it helps keep your home warm too. But because the stove is air-tight, it doesn't let any cold air from outside your home come in and make your home chilly.
Also, when you burn wood in the air-tight stove, it produces something called smoke. But because the stove is air-tight, the smoke can't escape into your home and make it smelly or unhealthy to breathe. Instead, the smoke goes up through a special chimney that is connected to the stove, and it goes outside so it doesn't bother you.
So basically, an air-tight stove is like a big, sturdy box that you can use to make a cozy fire inside your home. And because it's air-tight, it keeps your home warm without letting any chilly air or smelly smoke inside.