SOR - Smart Order Routing

Hello everyone!
I just came across a technical term named SOR (Smart Order Routing). Tried to google it but couldnt quite grasp it completely. i just understood that it is very useful if you want to find the best possible price across different exchanges so that buy orders can be bought at the lowest available ask prices and sell orders can be executed at the highest bids available. has anybody here used it extensively? if yes, could you please elaborate?

Well detailed... http://www.religarecm.com/article-sor-Id-29.aspx

http://www.omnesysindia.com/nestsor1.html

Is SOR useful for retailers or only institutional?

Seems it is useful for high volume traders in NSE & BSE.

Go through this case study : http://www.cio.in/case-study/kotak-securities-leverages-smart-order-routing-help-customers-stay-profitable