Both Nikon D80 and Samsung SL30 have 10.0 MP resolution sensors but Nikon D80's sensor is APS-C (23.6 x 15.8 mm ) and Samsung SL30's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Nikon D80'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 Samsung SL30.
Below you can see the D80 and SL30 sensor size comparison.
As seen above, Nikon D80 has a 13.5x Larger sensor area than Samsung SL30. 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.