S3 is "Sleep" and S4 is "Hibernate" mode. 

S4 is essentially the same as S5 (For systems where ACPI standards are applicable, Off Mode correlates to ACPI System Level S5 state) from a power consumption perspective. 

The S3 and S5 data for various configurations is available in the QuickSpecs or IT Eco Declarations per product. S3 is configuration dependent, while S4 and S5 do not vary by configuration.