According to the Upaniṣads, Brahman is both the immanent and the transcendent Reality. Having created the world, Brahman enters into it (vide Taittirīyopaniṣad 2.6) and controls it from within (vide Bṛhadāraṇyakopaniṣad 3.7.3-23). In this aspect it is called the ‘antaryāmin,’ the inner controller.
In Advaita Vedānta, the individual self is ultimately identical with the antar-yāmin. But in Dvaita and Viśiṣṭādvaita, the two are different.
In the Pāñcarātra school of Vaiṣṇa-vism, God manifests himself in four forms retaining the para or the highest form in his world called Vaikuṇṭha: vyūha (the four emanations), vibhava (incarnations), arca (manifestation through the image during worship) and antaryāmin (the inner controller). According to this school, the last is only a partial manifestation.