Unified Audit STANDARD ACTION vs SYSTEM PRIVILEGE

When setting up unified auditing what difference do the two options below make.

ALTER AUDIT POLICY CUST_AUDIT_POLICY ADD PRIVILEGE ALTER DATABASE LINK ONLY TOPLEVEL

vs

ALTER AUDIT POLICY CUST_AUDIT_POLICY ADD ACTION ALTER DATABASE LINK ONLY TOPLEVEL;

We are using CIS Baselines for configuration hardening and cant figure out what the difference between the two statements above