Both Panasonic ZS45 and Sony NEX-5T have 16.0 MP resolution sensors but Panasonic ZS45's sensor is 1/2.33 (6.08 x 4.56 mm ) and Sony NEX-5T's sensor is APS-C (23.4 x 15.6 mm ).
Since Sony NEX-5T'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 ZS45.
Below you can see the ZS45 and NEX-5T sensor size comparison.
As seen above, Sony NEX-5T has a 13.2x Larger sensor area than Panasonic ZS45. 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.