How does Online shopping sites like Flipkart track the search queries?

Once u make a search at that time they might save in there database, along with your ip address or mac address, cookie solution might not be correct because i believe once u clear your cookies you will still get same items

Thats called Retargeting the ads to the user. As said, cookies store the tags and then used by sites to display relevant content.

Using https://www.ghostery.com/(a chrome extension) you can easily find out the trackers behind any website. Flipkart uses a host of trackers to track user activity:-

Thanks for the A2A. Wikipedia defines this as @http://en.wikipedia.org/wiki/Behavioral_retargeting : Behavioral retargeting (also known as behavioral remarketing, or simply, retargeting) is a form of online targeted advertising by which online advertising is targeted to consumers based on their previous Internet actions, in situations where these actions did not result in a sale or conversion. Now coming to the point on how shopping sites like Flipkart do this: Whenever you take actions on the website a)Say you visit a Laptops Page or b)Visit Dell Insipiron Laptop product page or c)Add a laptop to your cart They make a 3rd party call to their advertisers ( Can be found via the ghostery plugin as someone mentioned in one of the answers) , and track your information(category you visited or the product you added to cart) via cookies. And when they see that you haven't bought that laptop, they feel if you are retargetted with the same product , there is a good chance you ll buy that laptop.