The document discusses the impersonal use of "se" in Spanish. It is used to talk about something without mentioning a specific person or agent. Some examples of impersonal constructions with "se" include "Se dice que..." (It is said that...) and "¿Aquí se permite fumar?" (Is smoking permitted here?). Additionally, "se" can be used with the third-person singular or plural form of a verb as a substitute for the passive voice in Spanish, where the agent performing the action is not mentioned.