dwandwa moha - its making (pravrutti) and breaking (nivrutti)

"Duality based delusion" that brings beings into "bandha" which is called pravrutti maarga that is caused by iccha, dvesha duality and bundle of desires. Freedom from this duality leads to "moksha" that is called Nivrutti maarga.

Lord Declares:
इच्छाद्वेषसमुत्थेन द्वन्द्वमोहेन भारत।
सर्वभूतानि संमोहं सर्गे यान्ति परन्तप।।7.27।।

iccha, dvesha samuthena, dwandwa-mohena, bharata
sarva bhutaani sammoham sarge yaanti parantapa.

By what arises from likes and dislikes, by delusion of duality O Bharata, all the beings are DELUDED completely (yaanti sammoham) originate (sarge) O Parantapa!

This is the secret of BIRTH (sarga or visarga or taking up agency of doer-ship and enjoy-er-ship). This is also called pravrutti maarga or going forward from the original source.... This is typical path of a BHOGI....

Then we know the story of cycle of going around and around within the world of spatial and temporal limitation.

But,

येषां त्वन्तगतं पापं जनानां पुण्यकर्मणाम्।
ते द्वन्द्वमोहनिर्मुक्ता भजन्ते मां दृढव्रताः।।7.28।।

yesham, tu, antagatam, paapam, janaanaam, punya-karmanaam
te, dwandwa-moha-nirmuktaah, bhajante, maam, dhrudha-vrataaha.

Those people, whose sins have come to an end, and of vitreous in deeds
they, being freed from delusion of duality, with firm conviction start worshiping ME. (The supreme unlimited self who is beyond all duality)

Why do they do so?
(Now Lord is stating the Nivrutti maarga the path that takes one back to the supreme reality or the path of a "YOGI")

जरामरणमोक्षाय मामाश्रित्य यतन्ति ये।
ते ब्रह्म तद्विदुः कृत्स्नमध्यात्मं कर्म चाखिलम्।।7.29।।

jaraa, marana, mokshaaya, maam, asritya, yatanti, ye
te, brahma tat viduhu, krutsnam-adhyatmam, karma, ca, akhilam

Those who strive, by surrendering to me (the supreme lord) for liberation from old-age and death, they know:
a. that brahma (tat brahma) "BRAHMA" (no other word can be used for this in any language)
b. all about atma (krutsham-adhyatmam)
and
c. all about action (akhilam karma)

साधिभूताधिदैवं मां साधियज्ञं च ये विदुः।
प्रयाणकालेऽपि च मां ते विदुर्युक्तचेतसः।।7.30।।

sah-adhibhuta-adhidaivam maam sah-adhiyajnam ca ye viduhu
prayaana-kaale api ca maam te viduhu, yukta-chetasaa

They "who have ever controlled and balanced minds", know ME, as
a. the manifested material elements and b. the Controlling Energy (adhibhutam adhidaivam sah)
and also ME as
c. the "sacrifice" (sah adhiyajnam)
even at the time of leaving the body - "Death"


Key points:

1. Delusion based on duality (dwandwa-moha) causes the "sarga" origination of the being into limited world.

2. Only those whose "sins" are nullified by doing purification based on Karma Yoga and if needed Raja Yoga practices will cross over the duality and make the faith firm on the Supreme Lord.

3. Such a pure soul who strives for "moksha" will know two things:
a. "That" Brahma, All about ATMA (self) and All about ACTION (this is called DHARMA - what can be done and what cant be done) This triad is of ultimate reality that is immutable.
b. The material BHUTAS, The DEVAS and about SACRIFICE (these three aspects are related to "this" MANIFESTATION of the WORLD which is mutable and ever changing)

4. He not only knows the above things, but also internalize/realize this "TRUTH" FIRMLY such that it is not even lost at the time of leaving the body (DEATH?).

While the LORD is "just being", the deluded one will go on a full circle of making up the delusion and breaking it to come back to the source at its own free will!