In his explanation of Sri Govind-tattva, Srila Bhakti Siddhanta Sarasvati Gosvami Prabhupada identifies Sri Baldeva as vaibhava-rupa (pastime form) of Lord Govinda. ‘Gah vindati iti govindah’ the word ‘go’ has several meanings including knowledge, senses, earth, cow and others. Sri Govinda manifests in five forms: 
svarupa or svayam-rupa: the original form. para-svarupa: the Narayana form. vaibhava-rupa: the pastime form. antaryami-rupa: the Indwelling Supersoul. arca-rupa: the Deity form. The svarupa or svayam-rupa, Vrajendranandana Govinda is the Cause of all causes.
 
isvarah paramah krisnah sac-cid-ananda-vigrahah anadir adir govindah
sarva-karna-karanam (Brahma-samhita 5.1)
The para-svarupa or para-tattva-svarupa is understood to be Sri Visnu-Narayana, the Lord of the paravyoma (the transcendental spiritual sky) and Vaikuntha.
 
Sri Baldeva Prabhu, the original Narayan, is the vaibhava-prakasa of Govinda. He is the original cause of all emanations. The propagating prime cause of individuality or the all-pervading function-holder of the Personal Godhead is also Baladeva – He is svayam-prakasa. Sri Baladeva’s color is white, different from that of Krisna. He carries a buffalo horn, which produces a louder sound than the flute of Krisna. Therefore He is known as Singadhrik (horn-holder). Sri Baladeva possesses qualities like Krisna. He is the fountainhead or prime source of the all-embracing, all-pervading and all-extending energy. The actual meaning of these definitions cannot be understood completely by using limited mundane terminology. Vibhu and Prabhu are interdependent. The one who is manifested as vaibhava-prakasa is Vibhu (the opulent manifested form), and the Divinity from whom He is manifested is Prabhu. There exists inconceivable non-distinction and distinction between Vibhu and Prabhu. Prabhu is Vasudeva and Vibhu is Sankarsana. Vibhu and Prabhu’s oneness aspect the third manifestation, is Pradyumna. Similarly, Their fourth manifestation is in the form of Aniruddha. These four constitute the original catur-vyuha in Dvaraka and are the origin of all other catur-vyuhas. Their second manifestation is the second catur-vyuha in the paravyoma or Vaikuntha. They are also pure and turiya (transecendental) like the original catur-vyuha. Baladeva, who is Sri Krisna’s vilasa form, is the Original Sankarsana. In the parvyoma or spiritual sky, Maha-Sankarasan is the svarupa-amsa Balarama’s own amsa-avatara. He is the source of the first purusa-avatara, Karanarnavasayi Maha-Visnu. He (Baladeva or His manifestation, Karanarnavasayi Maha-Visnu) is the cause of Rama, Nrisimha and other avataras, as well as Goloka and Vaikuntha, and is also the cause of cosmos. All of the mentioned five forms of Visnu are of the same nature. Any number of lamps can be lit from the original lamp, and they will be capable of burning all things. Similarly, the original lamp is svayam-rupa Sri Krisna and there is no difference in tattva (essence) ontologically between the second, third, fourth and fifth Visnu Deity or between one form and another of Visnu. There is only difference in the characteristics of Their pastimes. (The explanation of ‘Sri Govinda’ The compilation of lectures of Srila Bhakti Siddhanta Sarasvati Gosvami Prabhupada: 2nd Vol.)
 
Srila Krisnadasa Kaviraja Gosvami, while introducing the avataras of avatari (the fountainhead of avataras) Sri Krisna, writes in the 20th chapter of Madhya-lila of Sri Caitanya caritamrita as follows: Sri Krisna’s three different forms are:
 
svayam-rupa: the original form tadekatma-rupa: the same form, non-different from svayam-rupa but with different bodily features and specific activities
 
avesa-rupa: an empowered form Again, svayam-rupa is of two types: 
svayam-rupa svayam-prakasa ‘svayamrupe-eka krisna vraje gopamurti’ 
Again, svayam-prakasa is of two types: 
prabhava vaibhava sei vapu, sei akriti prithak yadi bhase
bhavavesa-bhede nama ‘vaibhava-prakase’
(Caitanya-caritamrita, Madhya 20.171)
 
"If one form or feature is differently manifested according to a different modes of features, it is called ‘vaibhav-prakasa’." 
vaibhava-prakasa krisnera sri-balarama
varna-matra-bheda, saba-krisnera samana
(Caitanya-caritamrita, Madhya 20.174) 
"The first manifestation of the vaibhava feature of Krisna is Sri Balarama. Sri Balarama and Krisna have different complexions, otherwise Sri Balarama is equal to Krisna in all respects."
 
In the 5th chapter of the Adi-lila of Sri Caitanya-caritamrita, Nityananda-tattva is explained as follows:
sarva-avatari krisna svayam bhagvan
tanhara dvitiya deha sri-balarama
eka-i svarupa donhe, bhinna-matra kaya
adya kaya-vyuha, krisna-lilara sahaya
sei krisna-navadvipe sri-caitanya-candra
sei balarama-sange sri-nityananda
(Caitanya-caritamrita, Adi 5.4-6)
 
"The Supreme Personality of Godhead, Krisna, is the fountainhead of all avataras. Lord Balarama is His second form. These two are one and the same identity. They differ only in form. Lord Balarama is the first expansion of Krisna and He assists in Lord Krisna’s transcendental pastimes. That original Lord Krisna appears in Navadvipa as Lord Caitanya, and Balarama appears with Him as Lord Nityananda."
 
Sri Balarama, who is the Deity of the sandhini potency, serves Krisna in His five forms of Maha-Sankarsana, Karanodakasayi, Garbhodakasayi, Ksirodakasayi, and Sesa.