Complex sentence: The stem is the component on a bicycle that connects the handlebars to the steer tube of a bicycle fork, primarily of the quill (sometimes called threaded) or threadless types, depending on bicycle's headset.
Split into simpler sentences: The stem is the component on a bicycle that connects the handlebars to the steer tube of a bicycle fork. Stems fall primarily into two types: the quill or threadless types, depending on bicycle's headset.