Both Sony WX500 and Panasonic ZS60 have 18.0 MP resolution sensors but Sony WX500's sensor is 1/2.3 (6.17 x 4.55 mm ) and Panasonic ZS60's sensor is (1/2. ).
Since Sony WX500'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 ZS60.
Below you can see the WX500 and ZS60 sensor size comparison.
As seen above, Sony WX500 has a infx Larger sensor area than Panasonic ZS60. 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.