Audit flags are the short names for audit classes. Audit flags are used in the audit_control file to specify machine-wide defaults for auditing on the machine. The audit_control file is described in The audit_control File.
You can make exceptions to the machine-wide auditing defaults for individual users. You put audit flags in a user's entry in the audit_user file. The audit flags are also used as arguments to the auditconfig command. See the auditconfig(1M) and audit_user(4) man pages.