That is, mudras induce the deity to be near the worshipper.
This mudra, formed with all five fingers of the right hand extended to touch the ground, symbolizes the Buddha's enlightenment under the bodhi tree, when he summoned the earth goddess, Sthavara, to bear witness to his attainment of enlightenment.
It is the mudra of the accomplishment of the wish to devote oneself to human salvation.
Mudras are used primarily to indicate the nature and function of the deity.
Vyakhyana Mudra; the Exposition of the DharmaMudra
This is also known as the six elements mudra, or the fist of wisdommudra, for it symbolizes the unity of the five worldly elements (earth, water, fire, air, and metal) with spiritual consciousness.