So, imagine there's a big metal stick coming out of the ground that can shoot water really far to put out fires. That's a fire hydrant! But sometimes, grown-ups need a special tool to turn the metal stick and make the water come out. That tool is called a hydrant wrench.
The hydrant wrench is like a big, strong key that fits onto the metal stick of the fire hydrant. When the grown-up turns the wrench, it makes the metal stick twist and turn, and then the water can come out. It's important for grown-ups because they need to be able to quickly and easily turn on the water to put out a fire.
Also, sometimes the hydrant wrench isn't very easy to turn. That's because it needs to be very sturdy and strong so it doesn't break. But the grown-up can use their muscles and strength to turn the wrench and make the water come out.
That's pretty much it! The hydrant wrench helps grown-ups to turn on the water from a fire hydrant so they can put out fires quickly and safely.