In Bhagavad-gītā, the Supreme Personality of Godhead says, ahaṁ sarvasya prabhavo mattaḥ sarvaṁ pravartate: [Bg. 10.8] Kṛṣṇa is the origin of everything. Vāsudevaḥ sarvam iti: [Bg. 7.19] Kṛṣṇa is everything. Mat-sthāni sarva-bhūtāni na cāhaṁ teṣv avasthitaḥ: [Bg. 9.4] everything rests in the body of the Lord, yet the Lord is not everywhere. Māyāvādī philosophers think that since the Supreme Personality of Godhead, the Absolute Truth, has become everything, He has no separate existence. Their philosophy is calledadvaita-vāda. Actually, however, their philosophy is not correct. Here, Bali Mahārāja was the seer of the Personality of Godhead's universal body, and that body was that which was seen. Thus there is dvaita-vāda; there are always two entities—the seer and the seen. The seer is a part of the whole, but he is not equal to the whole. The part of the whole, the seer, is also one with the whole, but since he is but a part, he cannot be the complete whole at any time. This acintya-bhedābheda—simultaneous oneness and difference—is the perfect philosophy propounded by Lord Śrī Caitanya Mahāprabhu.
(Srimad Bhagavatam------8:20:22-----purport).

The beginning of spiritual enlightenment is realization of impersonal Brahman. Such realization is effected by gradual negation of material variegatedness. Impersonal Brahman realization is the partial, distant experience of the Absolute Truth that one achieves through the rational approach. It is compared to one’s seeing a hill from a distance and taking it to be a smoky cloud. A hill is not a smoky cloud, but it appears to be one from a distance because of our imperfect vision. In imperfect or smoky realization of the Absolute Truth, spiritual variegatedness is conspicuous by its absence. This experience is therefore called advaita-vāda, or realization of the oneness of the Absolute.
(Sri Caitanya Caritamrta------1:2:5------purport).

The Māyāvādī philosophers, however, try to equate the minute living entities with the supreme living entity. Because they recognize no distinctions between them, their philosophy is called Advaita-vāda, or monism. Factually, however, there is a distinction. This verse is especially meant to impart to the Māyāvādī philosopher the understanding that the Supreme Personality of Godhead is the supreme controller. The supreme controller, the Personality of Godhead, is Kṛṣṇa Himself, but as a transcendental pastime He has accepted the form of a devotee, Lord Caitanya Mahāprabhu.
(Sri Caitanya Caritamrta------1:7:10------purport).

The purpose of the discussions in the Upaniṣads and Vedānta-sūtra is to philosophically establish the personal feature of the Absolute Truth. The impersonalists, however, in order to establish their philosophy, accept these discussions in terms of lakṣaṇā-vṛtti, or indirect meanings. Thus instead of being tattva-vāda, or in search of the Absolute Truth, they become Māyāvāda, or illusioned by the material energy. When Śrī Viṣṇu Svāmī, one of the four ācāryas of the Vaiṣṇava cult, presented his thesis on the subject matter of śuddhādvaita-vāda, immediately the Māyāvādīs took advantage of this philosophy and tried to establish their advaita-vāda or kevalādvaita-vāda. To defeat this kevalādvaita-vāda, Śrī Rāmānujācārya presented his philosophy as viśiṣṭādvaita-vāda, and Śrī Madhvācārya presented his philosophy of tattva-vāda, both of which are stumbling blocks to the Māyāvādīs because they defeat their philosophy in scrupulous detail. Students of Vedic philosophy know very well how strongly Śrī Rāmānujācārya’s viśiṣṭādvaita-vāda and Śrī Madhvācārya’s tattva-vāda contest the impersonal Māyāvāda philosophy. Śrī Caitanya Mahāprabhu, however, accepted the direct meaning of the Vedānta philosophy and thus defeated the Māyāvāda philosophy immediately. He opined in this connection that anyone who follows the principles of the Śārīraka-bhāṣya is doomed.
(Sri Caitanya Caritamrta------1:7:10------purport).