Lord Chaitanya is the only shelter for the forlorn, for the most fallen, and He is the only hope for those who are completely devoid of spiritual knowledge. The supremely powerful Lord Krishna is manifest in five different potencies. Although He is one without a second, in order to serve five specific spiritual purposes, He is manifest in five ways. Such diversity is eternal and blissful, in contrast to the conception of monotonous oneness. From Vedic literatures we can understand that the Absolute Truth, the Supreme Personality of Godhead, eternally exists with His diverse energies. Lord Chaitanya appeared with full diverse energies, and they are five in number; therefore Lord Chaitanya is said to be Krishna with diverse energies.
Out of the five diversities in the Absolute Truth, the form of Lord Chaitanya is that of the original Personality of Godhead, Krishna. Lord Nityananda is the manifestation of the first expansion of the Supreme Lord. Similarly, Advaita Prabhu is an incarnation of the Supreme Lord. These three—Chaitanya, Nityananda and Advaita—belong to the category of Visnu-tattva, or the Supreme Absolute Truth. Srivasa represents the pure devotee, and Gadadhara represents the internal energy of the Lord for the advancement of pure devotion. Therefore Gadadhara and Srivasa, although included in Vishnu-tattva, are dependent, diverse energies of the Supreme Lord. In other words, they are not different from the energetic, but they are manifest diversely for the sake of relishing transcendental relationships.
The whole process of devotional service involves a transcendental reciprocation in the relationship between the worshiper and the worshiped. Without such a diverse exchange of transcendental flavors, devotional service has no meaning.
In the Vedic literature (Katha Upanishad) it is stated that the Supreme Lord is the supreme living entity amongst all living entities. There are innumerable living entities, but there is one living entity who is the Supreme Absolute Godhead. The difference between the singular living entity and the plural living entities is that the singular living entity is the Lord of all. Lord Chaitanya is that supreme living entity, and He descended to reclaim the innumerable fallen living entities. In other words, the specific purpose of Lord Chaitanya's advent was to establish the Vedic fact that there is one Supreme Personality of Godhead predominating over and maintaining the innumerable personalities of all living entities. Because the impersonalist (Mayavadi) philosophers cannot understand this, Lord Chaitanya advented Himself to enlighten the people in general about the real nature of the relationship between the Supreme and the many entities.
In Bhagavad-gita Krishna's last instructions were that everyone should give up all other engagements and render devotional service unto Him. However, after Krishna's disappearance, less intelligent people misunderstood Him. They became contaminated with the Mayavadi philosophy, which produced so many mental speculators that people forgot the actual position of the Absolute Truth and the living entity. Therefore Lord Sri Krishna Himself, as Lord Chaitanya, again appeared to teach the fallen souls of this material world the way to approach Lord Krishna. The Bhagavad-gita teaches that one should give up everything and be done with this world of material attachment. A pure devotee of Lord Krishna and one who follows the philosophy of Lord Chaitanya are one and the same.
Lord Chaitanya's philosophy is that one should give up everything and worship God, Krishna. Krishna, as the Supreme Lord, the Personality of Godhead, spoke the same words, indicating Himself as the Supreme Lord. However, the Mayavadi philosophers misunderstood Him. Therefore Lord Chaitanya, to clarify the situation, reiterated Lord Krishna's message: One should not declare himself to be as good as Krishna but should worship Krishna as the Supreme Lord. We make a great mistake if we accept Lord Chaitanya as a conditioned soul. He is to be understood as the Supreme Absolute Truth, the Personality of Godhead, Sri Krishna Himself. It is therefore said of Lord Chaitanya in Chaitanya-charitamrta: "Krishna is now present in His five diverse manifestations." Unless one is situated in uncontaminated goodness, it is very difficult to understand Lord Chaitanya as the Supreme Personality of Godhead Himself. Thus in order to understand Lord Chaitanya, one has to follow the direct disciples of Lord Chaitanya—the six Gosvamis—and especially the path chalked out by Srila Jiva Gosvami.
The most astonishing fact is that Lord Chaitanya, although the Supreme Personality of Godhead, Krishna, never displayed Himself as Krishna. Rather, whenever He was detected by intelligent devotees as Lord Krishna and was addressed as Lord Krishna, He denied it. Indeed, He sometimes placed His hands over His ears, protesting that one should not be addressed as the Supreme Lord. Indirectly, He was teaching the Mayavadi philosophers that one should not falsely pose himself as 
the Supreme Lord and thereby misguide people. Nor should followers be foolish enough to accept anyone and everyone as the Supreme Personality of Godhead. One should test by consulting scriptures and by seeing the activities of the person in question. One should not, however, mistake Lord Chaitanya and His five diverse manifestations as ordinary human beings. Lord Chaitanya is the Supreme Personality of Godhead, Krishna Himself. The beauty of Lord Chaitanya is that although He is the Supreme Lord, He came as a great devotee to teach all conditioned souls how devotional service should be rendered. Conditioned souls who are interested in devotional service should follow in the exemplary footsteps of Lord Chaitanya in order to learn how Krishna can be achieved by devotional service. Thus the Supreme Lord Himself teaches the conditioned soul how He should be approached in devotional service.
There is a very nice song sung by Sri Narottama dasa Thakura, a great devotee and acharya in the disciplic succession from Lord Chaitanya. Narottama dasa sings: "When will there be transcendental vibrations all over my body simply by my hearing the name of Gauranga? When will tears incessantly flow from my eyes simply by my uttering the names of the Lord? When will Lord Nityananda have mercy upon me, and when will all my desires for material enjoyment become insignificant? When shall I be purified by giving up all contaminations of material enjoyment? And when shall I be able to see the transcendental abode, Vrnidavana? When shall I be eager to accept the six Gosvamis as my prime guidance? And when will I be able to understand the conjugal love of Krishna?"
The sankirtana movement inaugurated by Lord Chaitanya is a transcendental pastime of the Lord. The Lord says "By it I live simultaneously to preach and popularize this movement in the material world." The Lord was so kind that He accepted all kinds of people and delivered to them the most important factor in life: love of God. To fulfill His mission of bestowing love of God upon conditioned souls, Lord Chaitanya devised many methods to attract those people disinterested in love of God. After He accepted the renounced order, all agnostics, critics, atheists and mental speculators became His students and followers. Even many who were not Hindus and who did not follow the Vedic principles accepted Lord Chaitanya as the supreme teacher.
The fact is that both Krishna and Lord Chaitanya are the original Personality of Godhead. No one should try to eliminate Lord Chaitanya from Sri Krishna. In His form of Sri Krishna, He is the supreme enjoyer, and in His form of Lord Chaitanya, He is the supreme enjoyed.