Both Samsung HZ15W and Olympus TG-6 have 12.0 MP resolution sensors but Samsung HZ15W's sensor is 1/2.3-inch (6.08 x 4.56 mm ) and Olympus TG-6's sensor is (1/2. ).
Since Samsung HZ15W'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 Olympus TG-6.
Below you can see the HZ15W and TG-6 sensor size comparison.
As seen above, Samsung HZ15W has a 0.0x Larger sensor area than Olympus TG-6. 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.