How Search works in SharePoint || Basic Concept

Today we will try to check how search works in MOSS??
Once indexing is done MOSS 2 major server roles are responsible for search:

• Web Service
• Search Service
  Rest other are known as application role. These 2 roles can be configured in a single server or different server as per the farm architecture.

The basic action of a web server role is very simple. A user requests a web page by typing the web address in a browser. Out of two type of request GET request(Put request is used in entering request on server i.e. filling forms) makes a connection with web server, webserver send the requested page to the client in html format. Main thing is that SharePoint always makes a stateless connection. So once the request is fulfilled connection/session is disconnected and when the user makes another request different connection/session is developed . so if there is different web server in an environment different web server can serve request to single user.
Now the things come when a user do a search how it works:
a) When a user enter any query in the search column of a page. Web service of a web server will get this request.
b) Web server will send this request to search server/service. If in a farm webserver and search server lies in same server. Web service will send request to search service in same server itself.
c) Search server will look for that query in it index files.

Note: Index files are propagated to search server after the indexing/crawl done by index server and propagated to search server at this default location: C:\Program Files\Microsoft Office Servers\12.0\Data\Office Server\Applications. It can be changed acc to requirement.

Indexing/crawling concept can be check at my blog: How crawl works in SharePoint-how indexing work-basic concept
d) If search server get the result of the query in the index file.
e) It will pick the result of documents ,images etc. from the SQL , NAS etc.
f) Stream of result are provided in XML format to the Web service(web server).
g) Web service will convert the xml to html and return the result back to the client.