Mummers' play is like a little play that people perform during Christmas time. It's usually funny and silly, with characters like a king, a doctor, and a clown. They wear costumes and masks and act out a story with lots of jokes and singing.
When the mummers come to perform, they usually go from house to house and perform for the people who live there. They might ask for some food or drink, like a piece of cake or some hot cider, as a thank you.
The mummers' play has been around for a long time and is a tradition in some places. It's a way for people to have fun and celebrate together during the holiday season.