Both Olympus TG-5 and Panasonic FS25 have 12.0 MP resolution sensors but Olympus TG-5's sensor is (1/2. ) and Panasonic FS25's sensor is 1/2.3-inch (6.08 x 4.56 mm ).
Since Panasonic FS25'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-5.
Below you can see the TG-5 and FS25 sensor size comparison.
As seen above, Panasonic FS25 has a infx Larger sensor area than Olympus TG-5. 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.