Utility Workers Union of America
AFL - CIO Local 127

Society functions under a set of laws passed by legislators.  The workplace functions under a collective bargaining agreement negotiated by the union and the employer.  Both serve the same purpose: creating a set of binding rules on what is permitted and what is prohibited.  How does a contract get negotiated?  Sometimes the law under which a particular union and employer operate sets out specific procedures for reaching a collective bargaining agreement.  Or in the union contract itself, your union and employer may have agreed upon a set of rules for how the next contract is to be negotiated.  Exactly how the bargaining process shapes up will be determined in large part by whether you are in the public or private sector, and by the ground rules or history of the parties in your industry or workplace.
—Adapted from The Union Member's Complete Guide, by Michael Mauer