What Bruce has set forth is close to correct. However, I can't help but do a little legal nit-picking.
"Public benefit corporation" is a term used in California (among other places) as a term for non-profit corporations generally. (In New York State, we use the term "not-for-profit corporation" to mean basically the same thing as a California "public benefit corporation" (and we use the term "public benefit corporation" to mean something quite different -- a quasi-public corporation like the Metropolitan Transport Authority).) California public benefit corporations are not really "chartered by the state" (though New York ones like the MTA are chartered by the state). [Wikipedia isn't always a great source....]
In California, public benefit corporations may be created with or without members, or may convert from member to non-member and vice versa. However, a public benefit corporation with members is still a public benefit corporation.
(California also has "mutual benefit corporations" which are non-profit but never charitable (and are also not tax-exempt). Mutual benefit corporations are run for the benefit of their members, and not for the benefit of the general public.)
The term "member" can also be used to mean people (or organizations) who aren't really members. For instance, when you become a "member" of a museum, you are not becoming a member of the corporation (i.e., what some in ICANN-land have termed a "statutory member"). These non-statutory "memberships" are more for marketing purposes and have no governance role. "Statutory members" on the other hand, have a role in governance (which can vary markedly depending on the by-laws of the particular corporation.
Hope this helps.
Best regards,
Greg Shatan
(Speaking for myself, and not giving legal advice as I am not a member of the California Bar)