According to VeryWellMind, the Mandela Effect is a situation in which a large mass of people believes that an event occurred when it did not. The term was originated in 2009 by Fiona Broome, after she discovered that she, along with a number of others, believed that Nelson Mandela had died in the 1980s (when he actually died in 2013). It can be explained by false memories, confabulation, misleading post-event information, or priming.

Joe Rogan says he has a theory that the Mandella Effect is being used to alter history in front of our eyes without us noticing and then it is being used to gaslight the public into believing that certain things never happened.