According to the Yoga Sutras, “Dharana is the binding of the mind to one place, object, or idea.”
In other words, the training of the mind, or concentration. This is the beginning of your meditation practice. Dhyana or meditation is the culmination of Dharana and cannot be practiced without it. They are inseparable.
So, we fix our mind on something, concentrate on it to keep our minds from running all over the place.