If you’re currently working with SharePoint 2010 you know that
it’s not a power user task to build content roll ups spanning
across multiple sites. With SharePoint 2010 you can do that with
one web part and without requiring a knowledge of a query language,
at least in basic scenarios.

Check out the below video to see what else is available with
Content Search web part; highlights from the video:

1. Building Content Search query
2. Managing result types
3. Your results depend on the recency of the search crawl
4. Adding refiners to your query
5. Presenting your results as a list, slideshow etc

more in the video ..