Not sure what this is. To "clean up" your disk just delete the files you don't want. You can start by deleting any unwanted language files or using an app like Omni Disk Sweeper to list all the files on your drive.
OSX automatically defrags smaller files on the go. There is also iDefrag if you're really concerned. You can read more about disk fragmentation here (PDF).
To be honest OSX is quite good on self maintenance but you can help it along by repairing permissions occasionally and using a tool like Onyx. It's a shock to people switching over who are more used to battling to keep their PC's afloat but the Mac just wants to be used 🙂