The aim is to give you a more personalised searching experience - whether you want one or not!
Every time you perform any search through Google's search engine, and click on any of the results, Google will keep a track of your search clicking activities and will tailor the results it gives you next time to suit your interests mores.
This is already annoying, if, for example you have bought a pair of trousers from M&S and then every single web site you go on for the next few days shows you nothing but adverts for trousers from M&S. But you already have bought trousers, so why would you want to see them everywhere you go?
The way to stop this is to log in to your Google account and go to 'Account Settings'.
Find 'Services' and you will see a link whick lets you 'Go to web history'.
From this page it is possible to click on 'Remove all web history'
You can also 'Pause' your web history on the same page. This stops it from gathering any more information about you.
This should stop any more information being kept about your internet activity.