Extrinsic materials help you to understand, define or interpret the intent of legislation. For example:
Changes to the law are always being proposed and debated. In general a Bill, its Explanatory Memorandum, parliamentary debates (Hansard) and Second Reading Speeches are to be found through parliamentary websites.
In general, there are different types of Acts:
Principal Act - the original Act passed by Government. Also called a Numbered Act or Sessional Act
Amending Acts or amendments - these Acts make changes to the Principal Act and should be read together with the Principal Act
Reprinted Acts or reprints - incorporate in the Principal Act all the changes made by Amending Acts. Online, these are called consolidations or compilations
Acts in force - acts that have become part of law and deemed operational
Ceased Acts - legislation that is no longer in force, having been repealed, expired, revoked or superseded