It began with a few posts on 4chan, an extremely popular imageboard website developed in 2003. The term ‘imageboard’ basically classifies an internet forum that requires users to post images in order to start a discussion.
In 2017 an anonymous user claiming to have Q clearance within the US government (hence the shortened name QAnon from Q Anonymous) began to post information detailing a secret government investigation spearheaded by the President himself, Donald J Trump. They mentioned Robert Mueller, the man in charge of investigating Russian interference in the previous election, as being allegedly tasked instead by the President to be the head of this secret investigation. It highlights various political figures, like Hillary Clinton and former President Barack Obama and speaks of their involvement with the ‘deep-state’ of alleged sex-trafficking and paedophilia.
The posts contain a plethora of conspiracy theories primarily centered around outlining threats from the deep-state against Donald Trump. These theories range from harmlessly implausible (like that of JP Morgan sinking the Titanic to assassinate Col. Jacob Astor, Isidor Straus and Benjamin Guggenheim 108 years ago) to outlandishly dangerous.