On https://www.treasurydirect.gov/NP/debt/rss, we have three numbers:
Debt Held by the Public: $14,387,199,090,397.24
Intragovernmental Holdings: $5,552,709,700,473.24
Total Public Debt Outstanding: $19,939,908,790,870.48
It seems the latter number is often considered the U.S. national debt. What is the difference between the Debt Held by the Public and the Total Public Debt Outstanding?