Social media marketing involves using social media platforms like Facebook, Twitter, and Instagram to promote your startup's products or services, engage with potential customers, and build brand awareness. It can help startups reach a broad audience cost-effectively, share their story, showcase offerings, and drive traffic to their website. By creating a strong social media presence and leveraging tactics like targeted ads, influencer marketing, and engaging content, startups can boost sales, generate leads, and take their business to new heights.