Cyclo-Cross is a very specific type of bike racing. For the most part, the course is off-road but there are sometimes portions of pavement included in the course. You can expect to encounter grass, dirt, mud, gravel, sand, and a whole slew of other assortments and combinations. The races are based on a set time (measured by numbers of laps), not distance. Depending on your category, a race can be as quick as 30 minutes (for beginners), or as long as 60 minutes (for pros).
Check this video out of the Red Bull Velodux in 2017 in beautiful Estavayer-Le-Lac, Switzerland!
Got to be worth a go!