Psychosis is a symptom of schizophrenia...it's like the hallucinations delusions and cognitive difficulties etc but for schizophrenia there are more criteria...you have to be impacted for at least 6 months although you only need 1 month of psychosis. You just have to have reduced functioning at school work or social life during that 6 month period. Some people get psychosis and never develop schizophrenia. If your psychosis is less than a month it's brief psychotic disorder and if it's more than 1 month but less than 6 it's schizophreniform. There is also schizoaffective or bipolar with psychosis if you also have mood symptoms and even psychotic depression. If you don't really hallucinate but have delusions there is also delusional disorder but that is considerd a type of psychosis as well. These days they simply refer to all of these as the schizophrenia spectrum just like the autism spectrum ...