The Content Search Web Part (CSWP) is a Web Part introduced in SharePoint 2013 that uses various styling options to display dynamic content on SharePoint pages.

Content Search Web Part displays search results in a way that you can easily format. Each Content Search Web Part is associated with a search query and shows the results for that search query.

You can use display templates to change how search results appear on the page. Display templates are snippets of HTML and JavaScript that render the information returned by SharePoint. The information to be displayed gets inserted into the page in JSON format.

Content Search Web Part in SharePoint 2013