Yoga Sūtra Chapter Three verse 1

deśa-bandhaḥ-cittasya dhāraṇā ||1||

Concentration is binding the psyche to a place.

deśa - placebandha - bindingcitta - psyche; mind; heartdhāraṇā - concentration

Commentaries and Reflections

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.