Every application that you install on your android device creates cache. This cache seems to grow more and more as time goes by. It will take up a lot of your internal memory and also noticeably slow your gadget down. So it is better to remove the unwanted stuff.
You can download and install CM Security to do this. Open the application and click on the specified option shown in the screenshot below so you can clean up the junk on your phone, along with using the app for security services.