Direct objects answer the questions "who?" or "what?" and can be replaced by direct object pronouns like "it", "him", "her", or "them". Indirect objects answer the questions "to/for whom?" and can be replaced by indirect object pronouns like "me", "you", or "them". In Spanish, direct object pronouns come before the conjugated verb while indirect object pronouns come first if both are used in the same sentence. The document provides examples of direct and indirect object pronouns in Spanish.