"Hiciste" is the second-person singular form of the verb "hacer" in the preterite tense, which means "to do" or "to make" in Spanish. It is used to refer to an action that was completed in the past. For example, if someone asks, "¿Qué hiciste ayer?" it translates to "What did you do yesterday?" In everyday conversation, "hiciste" can be used in various contexts, such as discussing activities, tasks, or events. It is commonly used in relation to personal experiences, like "Hiciste la tarea" meaning "You did the homework." Understanding this verb form is essential for effective communication in Spanish.