SharePoint Search

Q.1. When to use the Content Search Web Part (CSWP) & when to use Content Query Web part (CQWP)?
Ans. The CSWP can return any content from the search index. Use it on your SharePoint 2013 sites when you are connecting to a search service and want to return indexed search results in your pages.
The CSWP returns content that is as fresh as the latest crawl of your content, so if you crawl often, the content that the CSWP returns is more up-to-date than if you crawl infrequently. If you need to display instant content or the refreshed version of content, use the Content Query Web Part (CQWP) instead.
Search crawls only the major versions of content, never the minor versions. If you want to display the minor versions of your content, do that by using a CQWP.
Some site collection administrators mark sites to not be indexed. Content marked in this way is not available in a CSWP. If you want to return results from a site that is marked to not index, use the CQWP instead.


Q2. What is SharePoint Crawled property?
Ans. The indexer passes and crawls your content and its metadata it adds the columns as crawled properties only. This means it has passed over your columns and the metadata assigned to each element. You do not have any control over the creation of “Crawled Properties”.
The crawl goes through your sites, lists and libraries to find your content and picks up the value in your columns and stores them as crawled properties.
Crawled properties are metadata (author , title , created etc)extracted from items while crawling SP content .


Q3. What is SharePoint Managed Property?
Ans. Managed properties are created by devloper/administrator and are mapped to one or more crawled properties.
Managed properties appear in refined search results and user can execute queries on these properties . Crawled properties can't be used for this.

Good Example:
Let me explain, pretend that your organization has many lists and libraries. Ok, maybe you don’t have to pretend. And in them, users created columns like “Customer Name” and “Client”. For the organization, these two columns represent exactly the same content, but not for search. For search, they are just crawled properties and two very different ones at that because they do not share the same name. On top of that, since they are only Crawled Properties, if someone searches for all documents where Client=Sharegate then they will find nothing at all. Because no search related feature works with crawled properties themselves, for that we will need to create a Managed Property called “Customer” and assign both of those crawled properties to it.

In some scenarios though, you may find that a Managed Property has already been created for your Crawled Property, automatically. Well that’s because as always, there are exceptions. If you create a Site Column and assign it to a list or library, when the indexer crawls over it, it will automatically create a Managed Property for it. Also, regardless of it being a site column or not, Managed Metadata columns will always have a Managed Property created for them.

http://en.share-gate.com/blog/understand-sharepoint-crawled-and-managed-properties-for-search



Q4. How a crawl work to index the content from MOSS?
Ans4. Main thing is that it can index, it can crawl anything stored in a server, in any format PDF, Zip, word, excel , txt, HTML, RTF, MS-Office etc. But to index the content other than office or Microsoft the index process is little more complicated but interesting.
1) When the scheduler for the crawl or index run, it will search for every place you have defined or what you called it a content source.
2) When it find a file in that, it will look on it extension. It will check in SharePoint SSP whether the type is defined to be indexed or not.
3) Now when the SharePoint confirms of file type it will look for a software/Ifilter to read this file. Ifilter is a software which will read a file. Every file need its own ifilter.
4) If SharePoint finds a ifilter for it. It will start opening this file and start scanning the file. It will remove certain words that are not required in search or not need to be indexed ex: 1 ,2 numerals etc.
5) After scanning the whole file it will index the content in index file with the pointer of name and location of the file.
6) Once a file is completed with full process. It will start for next file and with the same process as above.

https://ashishbanga.wordpress.com/2013/01/08/how-crawl-works-in-sharepoint-how-indexing-work-basic-concept/