Click to view a larger version. CC-BY 3.0 Mike Wirth & Dr. Suzanne Cooper Guasco, How Our Laws Are Made, https://commons.wikimedia.org/wiki/File:Visualization-of-How-a-Bill-Becomes-a-Law_Mike-WIRTH.jpg.
A legislative history of a bill is the sequence of steps or path taken to arrive at the final version of the law; the term is also used to refer to the documents reflecting that history. One of the purposes in compiling a legislative history is to try to ascertain what the legislature intended in authoring the bill, or the purpose and meaning of specific legislative language.
Different types of legislative history are given different weight.
Committee reports are generally given the most weight in determining legislative intent, because they are produced by the committee to which Congress has delegated the responsibility for detailed study and recommendation. Especially significant are Conference Reports, produced by Conference Committees appointed by the House and Senate to negotiate differences between House and Senate versions of a bill.
Changes of language in the bill as it is amended are given high significance.
Other documents, though less valuable than reports or the variant text of bills, may shed light on the context in which legislators considered the bill in question: