For a summary of the Initiative process see How to Qualify an Initiative on the Secretary of State web site. The web page includes a copy of Statewide Initiative Guide, a step-by-step information on the statewide initiative process.
A majority of electors must vote to approve the proposed amendments or revisions. If successful, the changes will take effect the fifth day after the Secretary of State files the statement of the vote for th election unless the language of the amendment/revision states otherwise. If conflicting measure are approved at the same election, then the provisions of the measure reciving the highest affirmative vote shall prevail. Cal. Const. art. IVII, §§ 1-4.
The initiative is the process that allows the electors to propose legislation and compel the legislature or the full electorate to vote on the measure. A referendum is the power of the electors to approve or reject all or parts of certain types of statutes. Both the initiative and the referendum process are methods of direct democracy. Propositions are the proposed legislation for either the initiative or the referendum.
As excerpted from Legal Research in California (5th ed. 2004)
"the people of California may directly add, repeal, or amend provision of the California Constitution or statutes," through ballot propositions. The ballot propositions "are prosed either by the Legislature or by citizens."
"Propositions directly from the people are proposed by petitions circulated for the [required] number of voter signatures. Propositions from the Legislature are adopted like other legislative measures." Propositions "propose either bond measures, constitutional amendments, or statutes that change existing statutes previously approved by initiative." Referenda are "propositions that allow the people to approve or reject legislative enactments." Initiatives are "propositions that propose legislative or constitutional changes." p.163.
The Initiative and Referendum Institute, a non-profit educational organization that provides explanation of the initiative and referendum, offer three general fact sheets:
as well as a California specific fact sheet.
L. Tobe Liebert, in Researching California Ballot Measures, 90 Law Libr. J. 27, explains the ballot measure process with information on locating documents, legislative history and legal challenges to ballot measures. Research tools and publications are provided in appendices.