Library folder in your home directory is an essential folder in OS X that stores application configuration and data. Since OS X Lion, this folder is hidden by default in Finder app. You access it in Finder using Option key together with Go menu. Or you can access it as per normal folder inside Terminal.
This “be safe” approach by Apple is not an issue for most users. But it is inconvenient when you need to access the folder for troubleshooting or for app development.
With OS X Mavericks, you can now have the Library folder permanently viewable in Finder.
Navigate to your home folder (/Users/<username>/) in Finder. Select from menu View > Show View Options. A model window will pop up with options to change the view settings.
At the bottom of the view options window, tick the checkbox Show Library Folder. This will unhide the Library folder in Finder app.