Testimonial (noun)

1. A statement expressing admiration or approval.
2. A statement given by a person to certify their experience of a product or service.

Origin:

Late middle english (in the sense "evidence given in court"): from latin testimonium, from testis "witness".

Examples:

1. He gave a testimonial on the company's website.
2. The testimonial was a glowing recommendation of the product.
3. I am going to use this testimonial in my advertising campaign.
4. He wrote a testimonial to the effectiveness of the new treatment.
5. The testimonial of the satisfied customer was read out loud in the court.