Reddit Ads is the platform's self-serve advertising system that lets marketers buy impressions, clicks, or conversions on subreddit communities. You can run banner ads in sidebars, sponsored posts in feeds, or negotiate direct sponsorships with subreddit moderators. Reddit audiences are highly engaged and specific by interest (r/programming, r/fitness, r/entrepreneur), making it valuable for niche products. Unlike Facebook (broad targeting), Reddit is community-first. Success requires understanding subreddit culture and posting authentic content that resonates.