Apple has its reasons to hiding away certain files from the average Mac user – after all, it’s difficult to break something you can’t see. But sometimes you need to see those files–or access the hidden hidden ~/Library folder–in order to fix something that isn’t working on your Mac.
Alternatively, you may need to make some space on your Mac and think that deleting some of these hidden files might be a good way to do so. In that case we have a number of tips in How to free space on a Mac as well as How to delete Other storage on a Mac, How to delete system data on a Mac and How to delete cache on a Mac: our advice is not to delete these hidden files unless you really know what you are doing though!
If you aren’t sure how to see how much disk space your Mac has read: How to check how much disk space you have.
Read more at Macworld.com