The nishkama way of work leads you to attain naishkarmya siddhi. Shri Krishna says in the Gita
न कर्मणामनारम्भान्नैष्कर्म्यं पुरुषोऽश्नुते |
न च संन्यसनादेव सिद्धिं समधिगच्छति || 3. 4
Man does not attain the state of naishkarmya by not doing any work, neither does he attain this siddhi by giving up works.
In the next verse, Shri Krishna says that no one can survive without doing work. This means, we have to continue to do our work, but do those in a manner which does not create karma for us. This way of doing work is called akarma (non-karma) in the Gita.
Let’s take a step back here. We work because we want certain results for ourselves. The desire for results motivates us to do work. This is kaama-prachodita (inspired by desire) or sakaama work. How is it possible to work without this desire as inspiration? If we give up on desires for results, how will we be inspired to do work? And second, why is doing work without desire a spiritual practice?
Shri Krishna says that akarma leads to the attainment of Param-pada (3.19). That defines its spiritual goal. Unfortunately, doing our work as akarma is not easy. Shri Krishna says that even the wise are baffled about what would be karma, what would be vikarma (wrong work) and what would be akarma (4.17). Why? Shri Krishna says that the way of karma is mysterious. Indeed it is so. We hardly ever know all the ramifications of our actions. We may think we are doing it right, but often we lose sight of the question, right for whom?
So what is the way to doing our actions as akarma? Would it not be simpler if we just did not do any work? Then we will not have to worry about karma, vikarma and akarma. Right? Wrong.
Some wise people do think that our deeds can easily be doshavat (18.3), that is, tainted, therefore, they should be avoided altogether. But that is not an opinion approved by Shri Krishna. He recommends doing work without personal attachment and desire for results (18.6). Shri Krishna even says that giving up on niyata (regulated) karmas is a kind of moha or delusion (18.7). There are two kinds of regulated work, shastra-regulated and svabhava-regulated. But let’s not go into those for now. Just realize, niyata karma includes all our work.
Why is doing our work with attachment and desire bad for us? It is bad because it creates karma-bandhan (bondage to karma). That means, we create karma-samskara for our present and future lives, creating an impediment to liberation.
There are two ways of doing work without personal attachment and desire for results. Karma-yajna and Karma-yoga. Karma-yajna is easier to understand than karma-yoga. If works are done in the sense of yajna (yajnaathart karma), then it becomes karma-yajna (3.9). Shri Krishna recommends this way of doing karma. It is not a straightforward subject, but you can simply think of yajna as a way to overcome greed.
Karma-yoga is more complex. But it is simple also. Because it is yoga, which means it is a way to connect with Shri Krishna. That is the defining idea. How can our works become a way to connect with Shri Krishna?
By offering all our works to Shri Krishna.
यत्करोषि यदश्नासि यज्जुहोषि ददासि यत् |
यत्तपस्यसि कौन्तेय तत्कुरुष्व मदर्पणम् || 9.27
शुभाशुभफलैरेवं मोक्ष्यसे कर्मबन्धनै: |
संन्यासयोगयुक्तात्मा विमुक्तो मामुपैष्यसि || 9.28
Shri Krishna says:
Whatever you do, whatever you eat, whatever yajna you do, whatever you donate, whatever you strive for, O Arjuna! offer that to Me. In this way, you will be free from all the good and bad results of your actions and have no bondage to karma, and in this way, you will connect your Atman in yoga, and become free from bondage to karma and attain Me.