Show Hidden Folders in Finder

Show Specific Folder

Mac OS X hides many directories so they can't be seen in Finder even though you can navigate to them in Terminal.
To make a hidden directory visible in Finder, open a Terminal window and enter:

sudo chflags nohidden DIRECTORYNAME

DIRECTORYNAME is the directory you want to unhide.  This will also unhide all child directories of that directory.

To hide the directory from Finder:

sudo chflags hidden DIRECTORYNAME

For more, see How to view Root directory and subdirectories in Finder?

Show All Hidden Folders

You can show all hidden folders in Finder by opening a Terminal window and entering the following:

defaults write com.apple.finder AppleShowAllFiles YES
killall Finder

The "killall Finder" command kills finder which then restarts automatically.  The alternative to issuing this command is logging out and logging in again.

To hide them all again:

defaults write com.apple.finder AppleShowAllFiles NO
killall Finder

You can also use AppleShowAllFiles TRUE or FALSE.

For more, see How to show hidden files and folders in Mac OS X Finder