used when you are expressing thanks or asking politely for something, to show that you are grateful to somebody 感激;感谢 I'd be obliged if you would keep this to yourself. 如蒙保守这个秘密,我将感激不尽。 - obliged to somebody for (doing) something
I'm much obliged to you for helping us. 承蒙相助,本人不胜感激。 - obliged to somebody
Thank you. We are very much obliged to you. 谢谢你。我们非常感谢你。