cbsa_level indicates if the cbsa_code represents a Metropolitan or Micropolitan area.
Metropolitan Statistical Areas have at least one urbanized area of 50,000 or more in population. Metro areas also include adjacent counties that have either a minimum of 25% commuting to the central county(s) or a minimum of 25% of employment in the county who commuted from the central county(s).
Micropolitan areas have at least one urban area of more than 10,000 but less than 50,000 in population. Micro areas also include adjacent counties that have either a minimum of 25% commuting to the central county(s) or a minimum of 25% of employment in the county who commuted from the central county(s).
See also:
cbsa_code- Data Dictionary