Yoga Sūtra Chapter Three verse 1

देशबन्धः चित्तस्य धारणा ॥१॥

deśa-bandhaḥ cittasya dhāraṇā ||1||

Concentration is binding the psyche to a place.

deśa - place, point, region, spotbandha - bindingcitta - psyche (the totality of the human mind, conscious and unconscious); mind; heartdhāraṇā - concentration

Commentaries and Reflections

Commentary by TKV Desikachar:

Prāṇāyāma leads to this.
Pratyāhāra, to see without the senses distracting or pulling the mind, and
Dhāraṇā, to see without the mind losing itself, because of colouring or expectations.
Dhyānam arises out of this.

Perhaps the best explanation of Dhyāna is given by Patañjali in the Yoga Sūtra Chapter Three verses One and Two, where he states that one must first fix the question (Dhāraṇā) and then link to it (Dhyāna).
One who is not able to fix the question is not able to succeed in Dhyāna.

Since Dhyāna cannot occur without an object of concentration,
there must be an area (Deśa) where you fix your mind.
So, first you have to fix or bind (Bandha) your mind on a particular place (Deśa), a chosen object; this is known as (Deśa Bandha as in YS C3 v1).
And second, the mind should establish a relationship with this object which should last, at least, for a moment.

Commentary by Paul Harvey:

Dhāraṇā is the process of ‘holding onto’ the object.
Dhyānā is the process of ‘linking with’ the object.
Samādhi is the process of ‘integration into’ the object.”
Reflections on Yoga Sūtra Chapter 3 verses 1-3