Just as assets can be either relationship property or separate property, debts may be classified as relationship debts or personal debts. The responsibility for relationship debts is shared but personal debts are the responsibility of the person who incurred them.
Relationship debts are debts incurred:
Personal debts are incurred to acquire or improve separate property or incurred before the relationship began or after it ended. Even though a debt may be in one partner's name only (say on one partner's credit card), that does not mean it is a personal debt - it will depend on the purpose for which it was incurred.
The property to be divided is the total value of the relationship property minus the relationship debts.