Continuouscrawls is a new feature in SharePoint 2013, it keeps the search index andsearch results as fresh as possible. With all new changes in 2013, a documentcan appear in the index within seconds of going through the content processingcomponent. By default, this is configured to run every 15 minutes. Oncea document is uploaded, it will get processed by the content processing subsystem on thefly. To configure Continuous crawl, Go to Central Admin>AppManagement>Manage Service Applications > Search Service Application>ContentSources>Right Click>Edit>Change the crawl schedule to ContinuousCrawl.
