Both Panasonic ZS50 and Canon SX240 HS have 12.0 MP resolution sensors but Panasonic ZS50's sensor is (1/2. ) and Canon SX240 HS's sensor is 1/2.3-inch (6.17 x 4.55 mm ).
Since Canon SX240 HS'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 ZS50.
Below you can see the ZS50 and SX240 HS sensor size comparison.
As seen above, Canon SX240 HS has a infx Larger sensor area than Panasonic ZS50. 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.