These documents, along with Command Papers, provide an amazing documentary store covering hundreds of years and many subjects.
House of Commons Papers cover a range of subjects and come from various sources. This is not an exhaustive list, but among others they include:
A Bill is a draft law, which needs to pass both the Commons and the Lords, then receive Royal Assent, in order to become an Act. A Bill is a draft Act of Parliament. To become law it has to be approved by both Houses. It is reprinted as many times as necessary on its passage through both Houses, in order to incorporate amendments. Bills are numbered serially within each Session, and each
amended version is given a new number. Bills in the Commons have the prefix HC and Bills in the Lords have the prefix HL. Not all Bills do become Acts. A useful guide to the way a bill progresses through Parliament is available on the Parliament website.
To see how bills in the current parliament are progressing, see the Bills before Parliament page.
The research units of the Commons and the Lords produce very useful publications which discuss various topics, including government bills, see the Research Publications page. Typical examples include a 'Standard Note' on the Data Retention and Investigatory Powers Bill and a Research Paper on the Modern Slavery Bill
The online full-text service, U.K. Parliamentary Papers has the widest collection of British Official Publications covering the greatest number of years.
The following printed indexes may help you track down a particular document or confirm a reference: