This is the 782nd most frequent German word.
karl
The German word "Karl" is a male given name, equivalent to "Charles" in English.
In this sentence, 'Karl' is used as a proper noun identifying a specific person.
Karl liest jeden Tag ein Buch.
Karl reads a book every day.
In this case, 'Karl' metaphorically represents someone behaving in a way often associated with people named Karl.
Das ist ein typischer Karl-Moment.
That is a typical Karl moment.
Here, 'Karl' refers generically to any person named Karl, used as a placeholder name.