htaccess explination

can you guys please explain what the following does?

RewriteCond %{QUERY_STRING} !.*track=.*
RewriteCond %{HTTP_COOKIE}  !.*trackc.* [NC]
RewriteCond %{HTTP_USER_AGENT}  !.*(googlebot|msnbot).* [NC]
RewriteRule ^index\.(html|php)$ [L,R=301]

also what does NC mean and , L, R
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It will redirect a request for or to as long as the query string (the ?something=something&somethingelse=somethingelse part) doesn't have "track=" in it and as long as the cookie doesn't contain the "trackc" string, and the client isn't a google or msn website crawler.

NC means to ignore case, in other words case insensitive, L means its the Last rewrite rule to follow in a chain and R specifies what code to return for the redirect, in this case a 301 http status code.

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AzurewaveAuthor Commented:
Hey there, can you just answer one last thing, what do you mean Last rewrite rule in the chain, if there are more rewrite rules after that it will ignore them?
It causes the current request to stop processing the rules.  However, note that at that point, you can sent a redirect to the client, so they make another request that starts to get processed again.  The reason I point this out is that the [L] flag is not something that will close a loop if one is created.  It will simply stop the rule processing and send the current redirect.
Not sure what I was doing here, but

"you can sent a redirect to the client, "  should read " the server sends the redirect to the client".
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