The definite article (al-) may identify a previously known referent or denote a class. In the first case, speaker and hearer share enough knowledge to recognize what is meant, even if its name has not been uttered in the immediate conversation.
ادْخُلِ السُّوقَ
Enter the market.
“The market” may mean the locally known marketplace; that is mental familiarity (ʿahd dhihnī). Generic use is different: the article can direct attention to a class rather than one historically known individual.
Treating every definite article as “that one individual” obscures important rhetorical contrasts.