In psychology, what is the 'Mandela Effect'?

Steven Biko died in prison that is what they remember but they connect it to Mandela.

Am a fan of Nelson Mandela just after I heard him deliver his speach

Honestly, Mandela Effect could be prevented if people check the news and reliable sources to confirm that it is really true and not believe everything they see on a particular source they see for the first time

huge meat stick, Thank you for that information.

I believe there's something to this because I have false memories too as do a lot of other people. There are groups based on this growing in number.