There are many important system files that Apple does not want you messing around with. Deleting any of these files or folders could irreparably mess up your system and would require a complete re-install of the OS. But of course there are other temporary files such as Cache files that don't need to be seen, as they just work in the background.
For example: .DS_Store - This file is created in every folder.
You can read the long-winded explanation of this file on Wikipedia.
But to summarize, It's an OS X hidden file to store custom attributes of a folder, such as the position of icons or choice of background image.
In this image you can see the translucent Hidden files.
To Show All hidden system files:
- Open “Terminal”
- Type either of the following (without quotes): Or "Copy and Paste" the line below.
- “defaults write com.apple.finder AppleShowAllFiles 1;killall Finder”
- “defaults write com.apple.finder AppleShowAllFiles TRUE;killall Finder”
- The Finder will restart then you will see the hidden files. They will be light and translucent.
To Re-Hide System Files:
- Open “Terminal”
- Type either of the following (without quotes): Or just Copy and Paste
- “defaults write com.apple.finder AppleShowAllFiles 0;killall Finder”
- “defaults write com.apple.finder AppleShowAllFiles FALSE;killall Finder”
- The Finder will restart and files will be hidden once more.
1 and TRUE denote the same value with the command string.
0 and FALSE denote the same value with the command string.
This will also make the Library file visible. It will be Transparent like all of the other hidden files. And once you re-hide the hidden files, it will disappear as well. It is a much better idea to use the previous tutorial to make it permanent.