Okay kiddo, an ancestral hall is a special room or building where people can remember and honor their ancestors - the people in their family who have passed away.
It's like a big space where you can see pictures or statues of your great-great-grandma and grandpa, and other relatives that you may have never met before.
People usually go to the ancestral hall on important days like a holiday or anniversary to pay respect to their ancestors by lighting candles, burning incense, and offering food or flowers.
Sometimes, people also use the ancestral hall to learn more about their family history, like where they came from and what their ancestors did for a living.
So, that's what an ancestral hall is all about. It's a place to remember and honor the people who came before us and helped create our family history.