Proposed bills are often categorized into public bills and private bills. A public bill is a proposed law which would apply to everyone within its jurisdiction. This is unlike a private bill which is a proposal for a law affecting only a single person, group, or area, such as a bill granting a named person citizenship or, previously, granting named persons a legislative divorce. After a bill is enacted, these bills become public acts and private acts, respectively.

Private law can afford relief from another law, grant a unique benefit or powers not available under the general law, or relieve someone from legal responsibility for some allegedly wrongful act. There are many examples of such private law in democratic countries, although its use has changed over time. 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.

In practice, a (technically) public act can have the effect of a private act by the addition of restrictions such as limiting the act's effect to areas falling within a certain population bracket.