A CBSA refers to either a metropolitan statistical area or a micropolitan statistical area. CBSAs comprise the central county or counties containing a large population core, plus adjacent outlying counties having a high degree of social and economic integration with the core. This forms the statutory definition of “local areas”.
For more information see 2010 Standards for Delineating Metropolitan and Micropolitan Statistical Areas here: https://www.govinfo.gov/content/pkg/FR-2010-06-28/pdf/2010 15605.pdf.