Metadata describe the content of a web page. The Page Metadata feature in Predictive Merchandiser lets you configure metadata using Use Predictive Merchandiser Templates.
When you trigger Predictive Merchandiser templates, the page metadata is added to the response payload, which looks like this: 
{
    "triggered": {
        "app": "test",
        "id": "5d9cd572-5928-4a16-a9de-5bab582538a2",
        "name": "example-template",
...
            "name": "Metadata of example-template",
...
            "inTemplates": ["5d9cd572-5928-4a16-a9de-5bab582538a2"],
            "pageMetadata": [{
                "metadata": {
                    "pageTitle": "Example page title",
                    "pageDescription": "Example description",
                    "pageKeywords": ["example"],
                    "imageUrl": null,
                    "pageUrl": null
                }
        }],
        "neverPublished": false,
        "staging": true,
        "published": false
    }
}
The Page Metadata feature also allows you to filter your facets by existing tags, clone the values of your facets, or select filters/facets with predefined metadata. If you have a large number of pages, you can also search your domain by Path URL using the URL Search. Predictive Merchandiser Page Metadata For more information, see Use Page Metadata.