A glottal (from glottis the area of the windpipe behind the tongue) fricative is a sound in which the flow of air out of the body is constricted by tightening the glottis — the part of the windpipe behind (below) the tongue which contains the vocal cords, creating a narrow opening through which the air passes before entering the mouth. English has two types of glottal fricative — voiceless /h/ as in happy and hello, and /ɦ/ which actually represent an entire class of voiced glottal fricatives — vowels (more on this here).