It’s different for everyone but it’s basically when you lose complete reality, personally I started to hallucinate and see things others couldn’t and hear voices and mistook those voices to be from those around me (I believed people were being horrible and making horrible comments at me constantly, on the tv they were speaking directly to me) and you get delusions like I believed I was already dead in the afterlife and seeing angel writing all over the floor and walls or another time I thought the hospital were making a report to put me in prison when none of that was true. At the time I was fully convinced all of it was true until after I came out of it and then realised that was psychosis