Individual historical revisionist theories are known as revisionist histories.
Historical revisionism is necessarily controversial, as it challenges widely-held beliefs. Evidence supporting revisionist histories is generally sparse or poorly documented. Belief in such histories are often based in belief of a conspiracy theory to explain a lack of documentation. An example is the theory that Franklin Roosevelt had prior knowledge about the attack on [Pearl Harbor]?, and allowed it to happen.
Some revisionist histories have become the generally accepted history as more information is revealed; for example, many history books of the past rarely mentioned, if at all, the relationship the European explorers, colonists, and later the United States had with the Native American population (who were referred to as American Indians or Red Indians). In the past, outside of Native American populations, very few would dispute the assertion that Christopher Columbus discovered America. As another example, throughout history slaves have not been considered as people, which has been reflected in the accepted histories of the time.