The Similar Results widget shows a list of assets (or "documents" in Search parlance) similar to the main asset displayed on a page. A typical use case for the Similar Results widget is showing a list of blog posts similar to the main blog post. For example, when viewing a blog post titled "Upgrade tips for Liferay DXP 7.1 to 7.2", similar blog posts like "Troubleshooting DXP upgrades" and "Upgrading Liferay Portal 6.2 to 7.1" would appear in a list next to the main article.
The first version of Similar Results supports Liferay Blogs, Message Boards, Documents, and Wikis. Support for additional asset types (whether Liferay or custom assets) is possible via an API (or more technically, an SPI called SimilarResultsContributor).
Similarity is determined based on the similarity of the text of specified fields. The logic used to determine what documents are similar can be configured per Elasticsearch's More Like This query parameters. The "main" asset on a page is determined by the URL of the page.
The widget ships with three display layouts (compact, list, and card) and supports customization through widget templates (aka: application display templates).