All files and directories that start with a dot . are hidden in OS X Finder.

Show:

1. Open Terminal.
2. Write defaults write com.apple.finder AppleShowAllFiles YES
3. Keep down alt and right click Finder.
4. Select "Relaunch".

Hide:

1. Open Terminal.
2. Write defaults write com.apple.finder AppleShowAllFiles NO
3. Keep down alt and right click Finder.
4. Select "Relaunch".

Source

• Quickly Show/Hide Hidden Files on Mac OS X Mavericks & Yosemite