If you say that you are indebted to someone for something, you mean that you are very grateful to them for something.
I am deeply indebted to him for his help.
我对他的帮助深怀感激。
Indebted countries, organizations, or people are ones that owe money to other countries, organizations, or people.
The treasury secretary identified the most heavily indebted countries.
财政部长明确指出了负债最多的一些国家。