Result Types and Display Templates
SharePoint on-premise and Classic Search Pages in SharePoint Online allow you to fully customise how results – and other Search Web Parts – are displayed.
These templates live beneath the Master Page Gallery in the Site Collection where the Search was performed.
Whenever you run a query from a Search Box, the results are rendered out with a Display Template by the Search Results Web Part.
Each kind of Search Result you get back can be displayed with a different Template.
The mapping between type of result item, and Display Template is achieved through Result Types.
You define these in the Site Collection where you perform the search, and not in Central Administration.
There are built in ones for all the default document types – Word, Excel, PowerPoint and many others.
Making your own templates require some HTML knowledge.
There’s a similar process to customise results from the Content Search, Search Box and Refinement Web Parts.