caches, logos, language files, universal binaries, system junk and trash. My questions area as follows:
-what are caches, logos language files and universal binaries?
-what kind of system junk does it clean?
1. Caches are just temp files used by the system - they are cleaned by system processes as part of the unix backend. It can't hurt to clean out the 3rd party caches, so this may save some space. Most Mac apps are pretty good about cleaning up after itself.
2. Logos and language files: if you use an English version of the OS, many apps will install alternate languages (korean, Russian, etc) - these can be safely cleaned out if you don't plan on changing languages. It can save 10-800 mb, based on the amount installed.
3. Universal: older versions of the OS and apps installed as a Universal version. This was done to allow support for PPC Based Macs AND intel versions. Since you have an intel Mac, this cleanup would strip out the universal version from the app. It can cut the app size by 50%.
4. Junk files: not sure what it removes, but I am sure it will include old .log, .tmp, and .hist files that apps have written during installs and updates.
Programs like these virtually never touch a user generated file, like docs or music. You should be just fine.