Very generally, here are the rules for determining what's community property and what isn't:
Community property includes all earnings during marriage and everything acquired with those earnings. All debts incurred during marriage, unless the creditor was specifically looking to the separate property of one spouse for payment, are community property debts.
Separate property of one spouse includes gifts and inheritances given just to that spouse, personal injury awards received by that spouse, and the proceeds of a pension that vested (that is, the pensioner became legally entitled to receive it) before marriage. Property purchased with the separate funds of a spouse remain that spouse's separate property. A business owned by one spouse before the marriage remains his or her separate property during the marriage, although a portion of it may be considered community property if the business increased in value during the marriage or both spouses worked at it. If separate property is commingled with community property during the marriage, it may become community property, either in part or entirely, depending on the circumstances.
Property purchased with a combination of separate and community funds is part community and part separate property, so long as a spouse is able to show that some separate funds were used. Separate property mixed together with community property generally becomes community property.