Public and private bills
Proposed laws, while they are being drafted, debated and amended in a legislature, are called bills: these draft laws are often categorized into public bills and private bills. A public bill is a proposed law which would apply generally throughout the relevant community or polity—or, in other words, it is a bill which is addressed to the community at large and applies to all persons within the jurisdiction (territory or power) of the relevant legislature. A private bill is a proposal for a law that will apply to, or effect a change upon, a particular subject identified by the law itself: in other words, it is a law that works upon a single person or group, or area, or organization, or relationship, et cetera.
The vast majority of bills proposed (and laws made) by modern parliaments (at least those operating in open, democratic societies) are public bills. This type of general, rule-focused, unbiased and impersonal legislating is: more generally applicable over time; more neutral as to particular people or companies (it does not seek to target particular persons for retribution, for example, or unfair benefices); more consistent with theories of the rule of law (it establishes, in advance, rules that will persist and apply to all, rather than one-off targeted legal changes); more suited to the protection of individual rights; more consistent with the separation of powers (under which doctrine judicial proceedings, rather than legislative fiats, determine individuals' rights and obligations); and more in accord with constrained legislative powers under constitutions.
Examples of private bills include bills granting a particular named person citizenship or some government office a legal right to particular revenue streams (and, more common before the wave of family law reform in the 1960s-70s, bills granting two named persons a "legislative divorce"). Private or subject-specific laws can afford their 'targets' relief from a general law that is otherwise applicable, grant a unique benefit or power not available under the general law, or relieve someone of legal responsibility for some wrongful act they have done, post hoc. There are many historical examples of private bills, even in democratic countries, although their use has changed over time.
In modern parliamentary practice, many bills are mixed in nature, having both private and public aspects: these are called hybrid bills. Some public laws set out such narrow terms of applicability that, while they are expressed in general terms, in practice they apply to only one person or organization, making them de facto private laws. This may be used (successfully or unsuccessfully) to maneuver around constitutional (written or unwritten) limits, or prohibitions imposed by international law.
A private bill is not to be confused with a private member's bill, which is a bill introduced by a "private member" of the legislature rather than by the ministry.