Oversteer is best described when the rear of the kart loses traction before the front of the kart. As a driver, you will have moments when the steering wheel is opposite lock, and that is the kart breaking into oversteer.
Oversteer can be felt on the entry to a corner, in the middle of the apex, or exiting a turn. When driving in the wet conditions, oversteer will be felt easiest on the exit of a corner when the kart wheel spins