How historians use a variety of sources of information to answer questions about the past

The variety of information is for example: 

archaeological find
primary sources, such as video recordings, sound recordings or testimonies of wittnesses
background and context information
linking dependencies and motivations (for example: what was the motivations for the crusades?)

they collect this information to provide a comprehensive account of the events, but they do take into account that any new information could change how we view something. 

History. The story told by those whom have been the victors of a never ending race of achievement. Historians have many sources to answer the question of the past such as libraries and online databases. Which have been revolutionized there research capacity being able to acquire months or even years of data in just a few clicks or taps on a digitized screen.