COP is the efficiency figure for a refrigeration system or compressor. Because a refrigerator moves heat rather than making cold, it can move more energy than it consumes, so COP is normally above 1. A closely related figure, EER (energy efficiency ratio), expresses the same idea in BTU/h per watt or watts per watt, and is common on air conditioners.
COP depends heavily on temperatures. The bigger the gap between evaporating and condensing temperature, the harder the compressor works and the lower the COP. That is why freezers have lower COPs than chillers, and why the same unit is less efficient in a 43 °C kitchen than in an air-conditioned shop. Compressor datasheets quote COP at defined test conditions for this reason.
For buyers, COP itself is rarely printed on a plug-in cabinet. What you usually see is energy consumption in kWh per 24 hours, which already combines compressor efficiency, insulation quality, door seals and fan power. COP is more useful when comparing compressors or condensing units for larger systems.