Dynamic range is a measure of the range of tones the sensor can capture. Cameras with low dynamic range will often show 'blown' highlights or blocked-in shadows. This test is carried out in controlled conditions using DxO hardware and analysis tools.
Dynamic range is measured in exposure values (EV). The higher the number the wider the range of brightness levels the camera can capture. This falls off with increasing ISO settings because the camera is having to amplify a weaker signal. Raw files capture a higher dynamic range because the image data is unprocessed.
Nikon 1 J5 dynamic range
JPEG analysis: The dynamic range of all four cameras is quite close, with the Nikon 1 J5 just edging ahead of the rest right up to ISO 800. At ISO 6400 and 12800, though, it's clearly worse than the others.
Raw analysis: When the raw files are compared the Nikon 1 J5 does well again, but this time it's overshadowed by the Panasonic GM5 and its larger sensor. The Sony RX100 III's low figures are unexpected.