A citation is a source link an AI answer attaches to a claim — the page the model retrieved and leaned on when composing its response.
Citation-first engines like Perplexity attach sources to every answer; ChatGPT and Gemini cite when they browse. Citations are the paper trail of AI recommendations: the pages a model cites decide the brands it names.
For brands, citations are the most actionable layer of GEO. You can see which review sites, comparison pages, and community threads the models actually read for your category — and make sure your brand is represented accurately on them.