For an attempt to a more philosophical answer, we may see: Jonathan Lear, Aristotle the desire to understand, (Cambridge UP, 1988), page 1:
Aristotle's Metaphysics begins [980a]:
"All men by nature desire to know. An indication of this is
the delight we take in our senses; for even apart from
their usefulness they are loved for themselves; and above
all others the sense of sight. For not only with a view to
action, but even when we are not going to do anything,
we prefer sight to almost everything else. The reason is
that this, most of all the senses, makes us know and
brings to light many differences between things."
Aristotle is attributing to us a desire, a force, which urges us on
toward knowledge. [...] Aristotle no doubt believed it was this desire that motivated
him to do the research and thinking that led to his writing the
Metaphysics, and he trusted in this desire to lead others to study it.
And see Met, 993a27: " The investigation of the truth is in one way hard, in another easy."
Thus, we may say that if we read understanding as a process: "the investigation of the truth", then complete understanding is the positive result of this process.
See also Lear, page 6:
Although 'to know' is an adequate translation of the Greek 'eidenai [εἰδέναι],' Aristotle used this term generically to cover various species of knowing. One of the species is 'epistasthai' (literally, to be in a state of having episteme) which has often been translated as 'to know' or 'to have scientific knowledge,' but which
ought to be translated as 'to understand.' For Aristotle says that we
have episteme of a thing when we know its cause [Post.An, 70b9: "We think we understand a thing whenever we think we are aware both that the explanation
because of which the object is is its explanation, and that it is not possible for
this to be otherwise."]
To have episteme one must not only know a thing, one must also grasp its cause or explanation. This is to understand it: to know in a deep sense what it is and how it has come to be. Philosophy, says Aristotle, is episteme of the truth.
But see Understanding for an overview of the many-sided issue: Explanation vs Understanding, understanding in the social sciences compared to the natural ones.