The word alambana means support, base or abode. In Yoga the mind is fixed on an object in the practice of concentration and contemplation. It may be a gross object, a subtle object or a sense organ, the ego-feeling, prakriti (original state), the self or god. Anyone of these can be an alambana, or support, on which the mind can be fixed in meditation.
According to the nature of the support, meditation is said to be of four different kinds – discursive (vitarka), reflective (vichara), blissful (ananda) and self aware (asmita). They differ in respect of the object of concentration. But there is one thing common to all of them, the fact that in all of them is a support or alambana on which the mind is fixed.
There is another state in which the mind is devoid of any support or alambana. That is very rare state in which comes about only when the mind is purified of all its impurities in the form of afflictions of the mind (kleshas) and traces of past experience (samskaras). That happens as a result of the higher, more skillful form of para-vairagya (detachment) that goes with realization of the true nature of the soul/self (viveka-khyati), which is the result of the absolutely pure state of the mind. In that state, the mind needs no support whatever for being still. It is called the state of nirbija or niralamba Samadhi. In it, alambana of all kinds are left behind.