California is one of a minority of "community property" states. In most states, property is divided in a divorce according to principles of "equitable distribution." Community property states divide all marital property equally between the parties, without regard to other issues. (Equitable distribution, on the other hand, strives to arrive at a division that is fair under all the circumstances, but not necessarily equal.)
In a community property state, each party is considered to own one-half of all marital property and to be responsible for one-half of all marital debt. Even if property is clearly traceable to one party, if it is acquired during the marriage (with very limited exceptions) it is community property. For example, if you open a savings account after you are married and deposit your weekly paycheck into that account during your marriage, those funds are still community property even though they were earned by you and put into an account in your sole name.
"Quasi-community property" is property that was acquired by either or both spouses (or domestic partners) while living in another state that, if it had been acquired while living in California, would be considered community property. For example, if you and your spouse lived in Florida for a year during your marriage and bought furniture there, it would be quasi-community property. Quasi-community property is treated by courts as community property in a California divorce.
Most divorces in San Diego County and elsewhere in California are resolved by settlement, not by trial. This means, as with many other aspects of divorce, that couples have the freedom to agree on property division between themselves rather than allow a court to divide their assets. Couples may reach agreement as to property division during their divorce, or may have done so earlier in a prenuptial or postnuptial agreement.