Both Sony NEX-3 and Panasonic ZS8 have 14.0 MP resolution sensors but Sony NEX-3's sensor is APS-C (23.4 x 15.6 mm ) and Panasonic ZS8's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Sony NEX-3'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 Panasonic ZS8.
Below you can see the NEX-3 and ZS8 sensor size comparison.
As seen above, Sony NEX-3 has a 13.2x Larger sensor area than Panasonic ZS8. 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.