which type of parenthetical element refers to specific nouns and begins with words like who, whom, and where?

The type of parenthetical element you are referring to is called a "relative clause." Relative clauses are used to provide additional information about a noun, and they typically begin with relative pronouns such as "who," "whom," "whose," "which," and "where." For example, in the sentence "My brother, who is a chef, is visiting," the clause "who is a chef" provides more information about "my brother."