Both Nikon D7000 and Fujifilm S4800 have 16.0 MP resolution sensors but Nikon D7000's sensor is APS-C (23.6 x 15.7 mm ) and Fujifilm S4800's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Nikon D7000'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 Fujifilm S4800.
Below you can see the D7000 and S4800 sensor size comparison.
As seen above, Nikon D7000 has a 13.2x Larger sensor area than Fujifilm S4800. 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.