Brahmā is in charge of something. Indra is in charge of something. The demigods, they're officers. They have no information. They say, "It is nature, nature, nature, nature." No nature. They are department. Department.
Indra is in charge of this cloud, how cloud is conducted, how rain falls there, and he's in charge of . . . water department, like that. Just like moon. Moon is in charge of lighting at night. Sun is in charge of lighting in daytime. Because it is darkness. The whole world is darkness.
So these demigods . . . similarly, Lord Śiva is in charge of destroying, tamo-guṇa. When there will be necessity of destroying this whole thing . . . because this world is like that. Everything that is created, that must be destroyed. Your body is created from the father and mother. Now it is being maintained. So creation and maintenance, and then the time will come, it will be destroyed.
So these three departments are there. So for creative department of this material world, Lord Brahma; for maintenance department, Lord Viṣṇu Himself; and for destruction, Lord Śiva. These are the guṇa avatāras, three, trinity.