Vorführer
Vorführer is a German noun with several related senses. In its basic sense, a Vorführer is a person who demonstrates something to others, typically in sales, training, or instructional settings. A showroom salesperson who explains product features to customers, answers questions, and gives demonstrations is commonly described as a Vorführer. The term derives from vor- (before, in front) and führen (to lead, to conduct).
A second sense refers to a demonstrator item: a device or vehicle used for demonstrations to illustrate
Usage and nuance: the primary sense is the person who conducts demonstrations, while the demonstrator-item sense