Official website:

A conker in England is a horse chestnut in America

The game called “Conkers” consists of two people playing against each other — each holds a leather string threaded through a conker. They take turns striking each other’s conker until it shatters.

What makes a conkers champion? — The Spectator

Excerpt from this article about this event last year:

“Last weekend, for the 54th time, hundreds of competitors met to compete for the title of world conker champion in the village of Southwick in Northamptonshire. King Conker was there to oversee the proceedings. Jasmine Tetley beat the men’s champion Ady Hurrell in the Grand Final to retain the title she won in 2019.”