One is said to be deluded if one thinks he/she is the doer of various actions instead of the body-mind-sense-complex.
prakṛteḥ kriyamāṇāni guṇaiḥ karmāṇi sarvaśaḥ |
ahaṅkāravimūḍhātmā kartā'hamiti manyate ||3.27||
Actions are performed in various ways impelled by guna of prakrti, the body-mind-senses. Deluded by the I-notion, one thinks, "I am doer."
Vimūḍhātmā is a person who think he/she is the doer of various actions because being deluded by the notion of "I" in this body-mind-sense-complex (ahamkāra). Because of this identification, the notion of "I" is limited in this body-mind-sense-complex with its modification (actions, thought, emotion etc). It can extent to hundreds of wrong notion about oneself (I am as good as this body, I am not smart, I am sad etc).
Ahamkāra - identification with this body-mind-sense-complex is there naturally. Whenever the body-mind-sense-complex is there, the identification is also there. Just like whenever the reflected medium is there, the projection of the sun appears in the medium itself. Identification itself is not a problem, in fact without "I-ness" in this body-mind-sense-complex, there is no activity possible for this person at all. But the problem lies on superimposition of qualities of the body-mind-sense-complex become one's own qualities which in turn causing complexity in the person. Because of this I-notion, one's mind is deluded in a hundred different ways, thinking that he/she is a doer/experiencer, even though it is the body-mind-sense-complex that perform actions and experience the results.
Next, the contrast between a jñānī and ajñānī (mentioned in previous verse), is explained.
tattvavittu mahābāho guṇakarmavibhāgayoḥ |
guṇā guṇeṣu vartanta iti matvā na sajjate ||3.28||
Whereas, Arjuna, the mighty armed! The knower of the truth of guna and actions is not bound, knowing that guna express themselves in guna (body-mind-senses-complex).
The wise person knows guṇakarmavibhāgayoḥ - the truth of body-mind-sense-complex and action. First fact: I am ātmā is different from guna (body-mind-sense-complex). Second fact: action is done by guna (body-mind-sense-complex), not me-ātmā.
An ignorance person takes the body-mind-sense-complex as oneself, and its actives to be one's own activities, whereas a jñānī knows he/she is different from the body-mind-sense-complex, and all activities do not belong to him/her. Jñānī identification with the body-mind-sense-complex is only as instruments to carry out the activities. Jñānī knows the truth of object (name and form) in the creation as nothing but modification of prakrti itself, therefore he/she can see action is nothing but a product of prakrti is in contact with another product of prakrti. Guna in the form of instruments (body-mind-sense-complex) engage in the activities, in contact with objects which are also guna - "guṇā guṇeṣu vartante". Because of this knowledge, a jñānī is not bound by actions which are done by body-mind-sense-complex.
Next Lord Krsna sums up five aspects of the karma-yoga attitude toward performing one's own duty.
mayi sarvāṇi karmāṇi sannyasyādhyātmacetasā |
nirāśīrnirmamo bhūtvā yudhyasva vigatajvaraḥ ||3.30||
Renouncing all actions unto me, with a mind that is discriminating, devoid of expectations with reference to the future and any sense of "mine-ness", without any anger or frustration whatsoever, fight (act).
"mayi sarvāṇi karmāṇi sannyasyā", - having renounced all actions unto me. The meaning of renunciation here in the context of karma is to offer all actions to the Lord. Doing what is to be done and do it with an awareness of Īśvara. In the commentary of Śankarācārya, example of how a servant does his/her various duty for the king without attachment. With this attitude one will do one's duty full-heartedly, either he/she likes or dislike it. It is being done because it needs to be done.
adhyātmacetasā, literally means one who endowed with mind. But It's not an ordinary mind, the mind with the ability to discriminate what is dharma and what is adharma; what is to be done and what is not to be done. This capacity is also called viveka-buddhi.
nirāśīh - one from whom all notions about the future have gone. It doesn't means a karma-yogī never plan for future, but he/she doesn't compromise the action to be done in the present with reference to what is going to happen in the future. Because a person who always plots for the further ambitions will inhibit him/her to do his/her duty in the present time.
nirmama means one from whom the mamatva (mine-ness) is gone. This notion of belonging will inhibit what is to be done. Because when we have the sense of ownership about a thing, we have a chance to choose to do thing with "my way".
vigatajvaraḥ - one who is free from anger. It doesn't means the karma-yogī never gets angry. When one being put in a situation/task which one doesn't like just like Arjuna's situation, one will get frustration, anxiety, grief, etc. This is not what we want to get as a karma-yogī, therefore the attitude of sameness - samatvam is the first thing one should build up, then one does one's duty without emotional torture.