The 15 Hive folder gets installed in the SharePoint front end server as a part of installation. It contains the following folders. The folder location is C:\Program Files\Common files\Microsoft Shared\Web Server Extensions\15
• ADMISAPI
• Bin
• Client
• Config
• HCCab
• Help
• ISAPI
• Logs
• Policy
• Resources
• Template
• UserCode
• Web Clients
• Web Services
SharePoint also creates 14 hive folder for backward compatibility.
Happy Share Pointing :-)