Bg 4.25

daivam evāpare yajñaṁ
yoginaḥ paryupāsate
brahmāgnāv apare yajñaṁ
yajñenaivopajuhvati

Synonyms: 

daivam — in worshiping the demigods; eva — like this; apare — some others; yajñam — sacrifices; yoginaḥ — mystics; paryupāsate — worship perfectly; brahma — of the Absolute Truth; agnau — in the fire; apare — others; yajñam — sacrifice; yajñena — by sacrifice; eva — thus; upajuhvati — offer.

Translation: 

Some yogīs perfectly worship the demigods by offering different sacrifices to them, and some offer sacrifices in the fire of the Supreme Brahman.

BG 4.25

Now Shri Krishna will describe different kinds of Yajna:

Different yajnas

•literal sacrifice (nishkama-karma-yoga),

•worship of devatas (sa-kama-karma-yoga –4.25 ab),

•offering atma to brahman(jnana-yoga –4.25 cd),

•restraining the senses (naishthiki-brahmacaris –4.26 ab),

•remaining indifferent to the action of the senses (Grihastha-brahmacaris –4.26cd),

•restraining the senses and pranas (jnana-yoga 4.27),

•practice of severe vows (karma, jnana-yoga, ashtanga-yoga 4.28),

•controlling the breath (yoga 4.29abcd), and

•restraining eating (yoga 4.29ef).

Daivam means unto devtas,

apare means some people,

yajnam -> those who are worshiping devtas,

yoginah paryupasate -> even those who are worshiping are yogis they are at one level connected to Krishna, they are not connected with Krishna at very high level but they are acknowledging that there are some higher powers. Brahmagnav, apare yajnam  -> there are others who perform yajna

yajnea-aivopa-ajuhvati -> they offer themselves to Brahman, they offer soul into brahman, i.e. they conceptualise that Brahman is the absolute truth and I have to merge into that. That is also a kind of sacrifice where they offer themselves. 

So the point is there are different kinds of sacrifices. So here Krishna is giving vision that how various religious activities in vedic culture are different kind of Yajna. 

After describing these various types of Yajna, Shri Krishna will describe purpose and recommend Arjuna what he should do.

Srila Prabhupad’s Purport: Those who are interested in material benefit worship the demigods by various sacrifices according to the Vedic rituals. They are called bahv-īśvara-vādī, or believers in many gods.

Bhau-isvara-vadi is called polytheism – how there can be many supreme? – different gods are having charge of different departments – they are under one Supreme God -> this is multi-level monotheism. Christians believe there are false god and true god and that is the reason when they would conquer some territory they will destroy all god worship there thinking that it is false god, but vedic understanding is that there are subordinate gods, there are assistant of Supreme God.