California observes a form of marital ownership of property common in states that border Mexico and which resembles partnership law. Consider a small sales business. It doesn't matter whether a partner is the star sales person or the one who orders and maintains the warehouse. Each partner's job is equally important. In that context community property has traditionally been fair to women as a homemaker's responsibilities are equally recognized to a wage earner's.
Generally, everything earned and/or owned prior to marriage is separate property. From the date of marriage to the date the couple separates the assumption is toward community earnings and ownership even if the title is solely in one partner's name. After separation anything earned or purchased is presumed to be separate.
There are some assets which may have a mixed character such as a retirement account. Some may have been earned before marriage, some during, and some after separation. The respective separate and community ownership will have to be determined.
There are of course exceptions to the presumption of community ownership. Gifts or inheritances from others outside the community are presumed to be the separate property of the recipient.
The most common question is, "What happens if funds are mixed?" Prior to 1984 the answer would have been that the community had received a gift. Today the assumption is that if the funds or property can be "traced" back to the date of acquisition the separate component is preserved. If separate funds are used to purchase or improve an asset, or reduce debt against an asset, they may be reimbursed during separation. Funds spent for bills or non-acquisition will generally not be reimbursed.