What is the definition of a "public record" under the California Public Records Act?

The Act requires that local and state agencies make their public records available for inspection. ( 6253.) A "public record" is defined as "any writing containing information relating to the conduct of the public's business prepared, owned, used, or retained by any state or local agency[.]" ( 6252, subd. (e).) The definition is broad and "`"intended to cover every conceivable kind of record that is involved in the governmental process[.]"'" (San Gabriel Tribune v. Superior Court (1983) 143 Cal.App.3d 762, 774, 192 Cal. Rptr. 415, quoting 6252, subd. (e).) But the mere possession by a public agency of a document does not make the document a public record. (City Council v. Superior Court (1962) 204 Cal.App.2d 68, 73, 21 Cal.Rptr. 896.)