Both Nikon AW120 and Fujifilm X-E2S have 16.0 MP resolution sensors but Nikon AW120's sensor is 1/2.3-inch (6.17 x 4.55 mm ) and Fujifilm X-E2S's sensor is APS-C (23.6 x 15.6 mm ).
Since Fujifilm X-E2S's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Nikon AW120.
One other difference between these two cameras that is worth mentioning is that Fujifilm X-E2S's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the AW120 and X-E2S sensor size comparison.
As seen above, Fujifilm X-E2S has a 13.1x Larger sensor area than Nikon AW120. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.