Facets are the core object upon which your standards are built. Facets define the type of object or option to be checked, such as database, Surface Area, and login. SQL Server ships with 74 facets, implemented as .NET assemblies, each with a unique set of properties.
All the objects for Policy Based Management are stored within the msdb database. You can get a list of the facets available by querying the dbo.syspolicy_management_facets table. Unfortunately, unless you want to write code to interact with Server Management Objects (SMOs), the only way to get a list of facet properties is to open each facet in SQL Server Management Studio (SSMS), one at a time, and view the list of properties.