Okay kiddo, so a church grim is a special kind of dog in stories and legends that comes from the country of England.
People believed that every church had a church grim that would protect the church and its people from evil spirits and bad things happening.
Sometimes, the church grim would even warn people of danger by making spooky sounds and appearing in eerie ways.
But don't worry, church grims were also known to be friendly and loved by the community. They were honored with special treats and even had their own holiday called "Hounds' Day" where they were celebrated with music and dancing.
So, basically, church grims are magical dogs that protected the church and were loved by everyone. Cool, huh?