Reviews in the context of YouTube and social media marketing are the public evaluations left by viewers, subscribers, or customers about a creator, product, or service. Reviews live on YouTube comments, community posts, review platforms, and third-party sites. Positive reviews build social proof, reinforce credibility, and lower the trust barrier for new viewers deciding whether to subscribe or buy. Negative reviews, handled openly, can also build trust when creators respond publicly and correct issues in front of the audience.