A grand is a true Piano, being a "PIANOFORTE" which is the original invention of Cristofori circa 17OO.  It has a refined escape mechanism and the hammer works with gravity which allows for the touch response and playing control of a "SOFTLOUD" that the later 18OO"s vertical piano does not possess.  Grands also have a true SOFT pedal which shifts the action so that the hammers strike only 2 of the 3 strings.