* Demonstrative pronouns point to specific things or people. Examples include "this," "that," "these," and "those." These are not used in the phrase.
* Indefinite pronouns refer to nonspecific people or things. Examples include "someone," "everyone," "nothing," and "anything." These are not used in the phrase either.
* Interrogative pronouns ask questions. Examples include "who," "what," "where," "when," and "why." "Who" is the interrogative pronoun in this phrase.
* Relative pronouns connect clauses and refer back to a noun or pronoun in the main clause. Examples include "who," "whom," "whose," "which," and "that." "Who" can also function as a relative pronoun, but not in this specific case.
In the phrase "Who are we meeting?" "Who" is functioning as an interrogative pronoun because it's asking a question.
Let me know if you'd like to explore other examples of these pronoun types!