The USNVC Hierarchy Explorer provides detailed descriptions of vegetation types in the U.S. USNVC Version 2.031 is the January, 2021 release of the classification. The USNVC is still under development for some geographies for details see Status of USNVC Vegetation Hierarchy.
General Citation for USNVC 2.03:
USNVC [United States National Vegetation Classification]. 2021. United States National Vegetation Classification Database, V2.031. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC. [usnvc.org] (accessed [day] [month] [year])