British Government Documents (History)

Rotuli Parliamentorum; Ut et Petitiones, et Placita in Parliamento. Earliest official records of the meetings of the Parliament; reigns of Edward I through Henry VII (1278-1503). 

• Translated and easy to read! Parliament Rolls of Medieval England. Reproduces the rolls in their entirety, as well as a substantial amount of material never previously published, together with a full translation of all the texts from the three languages used by the medieval clerks (Latin, Anglo-Norman and Middle English). Includes an introduction to every parliament known to have been held by an English king (or in his name) between 1275 and 1504, whether or not the roll for that parliament survives. Appendices of supplementary material are also provided.
   
• Also available in the databases Eighteenth Century Collections Online and Making of the Modern World; supplemented by Rotuli Parliamentorum Anglie Hactenus Inediti MCCLXXIX-MCCCLXXIII (DA 20 .R912 v. 51), which contains Parliament Rolls for 1279-1373 (omitted from the first source). Please note that the original editions are in Latin, Medieval English and Norman French.
   

• Chancery Rolls - Medieval source material.

Parliamentary debates (often referred to as Hansard, the publisher since the nineteenth century) are records of what is said in Parliament, roughly equivalent to the U.S.'s Congressional Record. Only since 1909 has Hansard been a verbatim report and official publication; before then, publications were based on secondary sources such as newspaper accounts. See this link from Parliament for more information and this guide from the University of Missouri.

• Pre-Hansard Debates:
  • 1066-1660. The Parliamentary or Constitutional History of England; From the Earliest times to the Restoration of King Charles II. 
  • 1066-1803. The Parliamentary History of England from the Earliest Period to the Year 1803 (Also known as Cobbett's). 
  • 1668-1741. A Collection of the Parliamentary Debates in England, from the year 1668 to the Present Time.
• Hansard:
  • 1803-1820. Parliamentary Debates from the Year 1803 to the Present Time.
  • 1802-Present. The Parliamentary Debates (Hansard Online). 

Journals are the official records of what is done in Parliament, roughly equivalent to the U.S.'s Daily Digest of the Congressional Record. The provisional records that are the basis for the Journals are Votes and Proceedings of the Lords. See this link from Parliament for more information.

• 1547-1699, 1830, House of Commons. British History Online
• 1837-present, House of Commons. Official website.
• 1509-1793, 1830-1832, House of Lords. British History Online.
• 1997-2017, House of Lords. Official website.

An Act of Parliament is a law. See this link from Parliament for more information.

• Ancient Laws and Institutes of England: Comprising Laws Enacted Under the Anglo-Saxon Kings... NOTE: Contains Latin and Anglo Saxon texts translated into English; texts in Latin, notes in English and some Anglo-Saxon texts in the runic alphabet.
• 1235-1713. Statutes of the Realm. 
• 1215-1785. Statutes at Large. 
• 1642-1660. Acts and Ordinances of the Interregnum.
• 1807-1869. Statutes of the United Kingdom of Great Britain and Ireland. 
• 1866-2006. Public General Acts and General Synod Measures.
• 1988-present. Official site.

See this PDF file from Duke University for a very detailed guide to English legal history.