What is actually difference between the character of Dr. Jekyll and Mr. Hyde?

Fggr. Jekyll confesses to Utterson that he has for a long time been fascinated by
the duality of his own nature and he believes that this is a condition that
affects all men. His obsession with his own darker side gives the novel its plot
but also its profound, psychological implications. Even before the climax of the
story in which it is revealed that Hyde and Jekyll are the same person, the
duality of their personalities creates a tension between the good, social Jekyll
and Hyde who seems to revel in causing harm and mayhem, and it looks like it
is Jekyll who will be overtaken somehow by Hyde.
One of the most interesting things about Jekyll’s transformation is its
psychological aspect. Hyde is portrayed as an evil-looking dwarfed man with a
violent temper, while Jekyll is a respected man of science, good-natured and
leader of his circle of friends. Not only are these men two halves of the same
person, but Jekyll describes them as polar opposites, one good and the other
evil. What does it mean, then, that once Hyde exists that he slowly seems to
take over, to destroy Jekyll. Is Jekyll’s theory of good and evil too neat and
clean? Hyde's takeover of Jekyll seems to suggest a less clear-cut explanation,
in which the human condition is not in fact double but rather one of repression
and dark urges, and that once the repression of those dark urges eases or
breaks it becomes impossible to put back into place, allowing the "true", dark
nature of man to emerge.
Jekyll’s disorder also reflects on the other characters, and raises the question
of just how upright, moral, and governed by reason they truly are. Utterson for
example is introduced as a lawyerly, kind man, and seldom seems to stray from
that description. But his character is so rigid and unmoving, and even
impersonal, that one could imagine he too is strenuously repressing a world of
darker urges.|