Cyclo-Cross (CX, cross or cyclocross) is a type of bicycle racing usually in the fall and winter. The track is usually in a field with lots of obstacles like sand, hills, stairs, streams, and jumps.
CX bikes make great bikes for city riding too. CX bikes have wider tires with tread, drop handlebars, and can take a beating. Just the thing you need for getting around the city. Many people who commute or ride mostly in city settings have switched to a CX or gravel bike.