CANONIZATION OF THE HEBREW BOOKS

Please answer the following question in about 2-3 paragraphs. Write as precisely as possible.
What does it mean the Hebrew Testament was canonized? Canon is an important word and designation? What does it mean? Who got to say what did and did not belong? (Think in terms of council) What do we do with new findings from archeology like the Dead Sea Scrolls? Are those as valid as others? What about those left out of the canon? Should we still consider them?