What are the differences in the rights between a civil union and marriage?

The propositions passed to ban gay marriage (which I disagree on), and others have told me that gay couples can have civil unions and have the same rights as married couples- I suspect that isn't true though. Can someone provide more information on differences (if any) between the rights of a married couple and the rights of a civil union couple?What are the differences in the rights between a civil union and marriage?
Any proposed statute could only affect state rights, not federal. Federal issues include taxation, testimonial priviledge, inheritance taxes. Other issues involve the private sector. Insurance companies, for instance, recognize marriage but cannot be forced to recognize other groupings. Private hospitals will recognize the rights of a spouse of an unconscious person, but need not recognize unions. Pension rights are similar. What are the differences in the rights between a civil union and marriage?
This depends on what a civil union is defined as by the state.





A civil union can be merely an acknowledgment of next of kin or it can offer all the benefits of marriage, except the name.