How does Continuous crawl work? And how does it differ from Incremental craml?
Continuous crawling helps to keep SharePoint content significantly more up to date. Continuous crawls are only available for Content Sources that use the SharePoint Sites content source type.
Unlike full and incremental crawls, multiple continuous crawls can run at the same time. Also, a continuous crawl does not process or retry items that return errors in order to improve speed.
It has got it's own advantages over Full/Incremental crawls. You can look at the detailed article at http://www.surfray.com/blog/2013/05/28/continuous-crawls-in-sharepoint-2013
Continious Crawl is introduced in SharePoint 2013. It helps in ensuring freshness of results. There are many articles where you can look into details.
let me know if more help is required.
Continuous crawls crawl SharePoint sites frequently to help keep search results fresh. Like incremental crawls, a continuous crawl crawls content that was added, changed, or deleted since the last crawl. Unlike an incremental crawl, which starts at a particular time and repeats regularly at specified times after that, a continuous crawl automatically starts at predefined time intervals. The default interval for continuous crawls is every 15 minutes. Continuous crawls help ensure freshness of search results because the search index is kept up to date as the SharePoint content is crawled so frequently. Thus, continuous crawls are especially useful for crawling SharePoint content that is quickly changing.
A single continuous crawl includes all content sources in a Search service application for which continuous crawls are enabled. Similarly, the continuous crawl interval applies to all content sources in the Search service application for which continuous crawls are enabled.
You cannot run multiple full crawls or multiple incremental crawls for the same content source at the same time. However, multiple continuous crawls can run at the same time. Therefore, even if one continuous crawl is processing a large content update, another continuous crawl can start at the predefined time interval and crawl other updates. Continuous crawls of a particular content repository can also occur while a full or incremental crawl is in progress for the same repository.
A continuous crawl does not process or retry items that return errors more than three times. A "clean-up" incremental crawl automatically runs every four hours for content sources that have continuous crawl enabled to re-crawl any items that repeatedly return errors. This incremental crawl will try to crawl the item again and then will postpone retries if the error persists.