Both Nikon D5600 and Canon 77D have 24.0 MP resolution sensors but Nikon D5600's sensor is APS-C (23.5 x 15.6 mm ) and Canon 77D's sensor is APS-C (22.3 x 14.9 mm ).
Since Nikon D5600'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 Canon 77D.
Another difference between these two cameras is that Nikon D5600's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the D5600 and 77D sensor size comparison.
As seen above, Nikon D5600 has a 1.1x Larger sensor area than Canon 77D. 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.