Both Sony A6300 and Nikon D610 have 24.0 MP resolution sensors but Sony A6300's sensor is APS-C (23.5 x 15.6 mm ) and Nikon D610's sensor is Full frame (35.9 x 24 mm ).
Since Nikon D610'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 Sony A6300.
Below you can see the A6300 and D610 sensor size comparison.
As seen above, Nikon D610 has a 2.4x Larger sensor area than Sony A6300. 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.