Demonstrator (noun)

1. A person who participates in a protest or rally to show support or opposition to a cause.
2. A person who shows or explains the working of a product or piece of equipment.

Origin:

Mid 17th century: from latin demonstrator, from demonstrare "point out, demonstrate".

Examples:

1. The demonstrators marched through the streets to call for political change.
2. The demonstrators held signs and shouted slogans to raise awareness of the issue.
3. The demonstrator gave a clear and concise explanation of the product's features.
4. The demonstrator was able to show the customers how to use the device.
5. The demonstrator was able to provide hands-on demonstrations to engage with the audience.