There are many different processes utilized depending on the specific artist/studio.
Usually it goes something like this:> create concept art > create high geometry > retopolgize high geometry into low geometry > test rig and refine low geometry until valid > bake high geo onto low > create textures.
Persoanlly I do it like this.> create concept art > create proxy shape of character > cut it up much like in >>523153 > refine resulting skeleton several times until it supports compelete motionrange>
Find a pose midway trough the motion range where joints are bent at a resting angle > work out and rig geometry that can deform flawlessly across the entire motionrange of each joint >> generate base for high geometry based on shape of resulting proxy > send to sculpting software and sculpt details > retopologize the high geometry into low > skin wrap resulting lowpoly to already skinned proxy>
clean up and adjust for any remaining weighting issues> bake textures > create additional textures send to game engine >
realize all bones points in the wrong direction because of axis order inversion conversion > flip table > have a smoke if at work, rage fap if at home > start correcting.