I appologize if this hasnt already been answered, i didnt eally read all the posts :XD: anyways. it clears the temporary files. what these are, is saved data from every website youve ever visited. it saves just a little bit, including passwords, so that next time you visit, it loads that much faster after you deleate them, the first time you visit the next webpage, it may run a little bit slower, but the time after that, it will run just as it did before. The thing thats good about this, is thoes particular webpages you visited once 4 years ago and will never visit again.. well your computer dosent know that. your computer is still wasting space trying to know a little bit about that webpage. so your gettin rid of that data, and never gonna get it back. trust me. everything ccleaner does.. is in fact. good hope it makes sence