Off page optimization is a technique which comes in process when Your website in Google and all other search engine like yahoo and MSN  indexed . First I clear the difference between cache and index. Cache  means that a search engine visit your website but not store in their database and index means that now your website is in search engine database.

When you search for a keyword search engine give result in a cache copy of  website. So after search engine index ur website try to bring some traffic on it. Now the term Off page come.

For more details visit http://seoranktoday.com/