Single axle describes a trailer’s running-gear layout, while ATV utility trailer usually describes a trailer intended to work with an ATV. An ATV-towed trailer may itself have one axle. The meaningful differences lie in the exact trailer’s body, coupling, running gear, handling features, and permitted operating conditions—not in two mutually exclusive labels.
The phrase ATV trailer is also used for a trailer that transports an ATV as cargo. That is a different role from a work trailer pulled by an ATV. Establish which role is intended before interpreting a product description, rating, or feature such as a ramp or tipping tub.