Both result types and design templates are new concepts introduced in SharePoint 2013. Kate Dramstad, a program manager from the SharePoint search team at Microsoft, describes both concepts in a single, easy-to-remember formula: result types + design templates = rich search experience.
When we perform a search we get back results. Some results are documents, others are pictures, SharePoint items, or just about anything else. Up until SharePoint 2010, all results, no matter which type they were, looked quite the same. Take a look at the following screenshot showing a results page from FAST for SharePoint 2010:

The results are dull looking, can't be told apart, and in order to find what you are looking for, you have to scan the results up and down with your eyes and zero in on your desired result.
Now let's look at how results are displayed in SharePoint 2013:

What a difference! The page looks much more alive and vibrant, with easy distinguishing of different...