The h sound is unvoiced, and the vocal cords do not vibrate during the production of this sound.
To create the h sound, the deep back of the tongue slightly constricts within the throat. The upper/front part of the tongue as well as the lips will often move into the shape of surrounding sounds at the same time as the h sound is being produced.
A common error ESL/ELL students make is overproducing this sound by constricting the tongue too much within the throat or by voicing the sound.