A proper name (ʿalam) brings a particular individual before the hearer by a name assigned to that person. “Zayd” identifies by name, whereas “the man who came yesterday” identifies by a circumstance or description.
Naming works especially well when the hearer already knows the bearer of the name. It is designed to single out the individual, not merely a passing attribute. But an unfamiliar name may fail to identify anyone for a particular audience; a relative expression or description may then communicate better.
Grammatical definiteness and successful recognition by an actual listener must therefore be distinguished.
Depending on context, naming may honor, disparage, express familiarity or seek blessing; these effects do not follow automatically from grammatical proper-noun status.