Any financial commitment undertaken, most commonly in relation to repaying money.
For example the obligation to repay a bond - together with related interest - or the obligation to repay other borrowings or other debt.
This type of obligation is sometimes known as a 'debt obligation'.
More generally, any legally binding financial or non-financial commitment.
These may be contractual obligations, or other legally binding obligations.
More broadly still, any type of commitment, whether or not it is legally binding.