What is the difference between psychosis and neurosis? Given such a sentence by a Test of English as a Foreign Language textbook,


  Mental disorder include psychosis and neurosis.


I googled and found a page

In introduction, the pages says,


  Psychosis and neurosis are terms used to describe mental conditions. Sometimes these words are used interchangeably to refer to the same condition.


Only what I clearly could deduct from the page is psychosis is brought about particularly by the use of alcohol and illicit use of drugs and their withdrawal.

Could anyone support me to distinguish these two symptoms more clearly ( and hopefully in a simpler way? )
Short answer
Psychosis can result in a loss of a sense of reality. Neurosis leaves the person suffering in contact with the here and now. Further, neurosis is an old term and was used as an umbrella term. Now its use has declined and rather more specific diagnoses are used.  

Background
 - Psychosis is according to Medicine Net:


  [A] mental illness that markedly interferes with a person's capacity to meet life's everyday demands. [It is] a thought disorder in which reality testing is grossly impaired. Symptoms can include [hallucinations, such as] seeing, hearing, smelling, or tasting things that are not there; paranoia; and delusional thoughts. [...] Psychosis can occur as a result of brain injury or disease, and is seen particularly in schizophrenia and bipolar disorders. 



Neurosis is according to Indiana University:



  [A] disturbing psychological disorders that still let the sufferer remain in contact with reality. This term plays a central role in Freudian psychoanalysis. In Freud's theory "neurosis" means "a personality or mental disturbance not due to any known neurological or organic dysfunction [brain or body problem]" (Reber, 1985). Freud used it as a label for a group of related symptoms of psychological problems that are distressing and painful. Unlike psychoses, which are psychological disorders that severely distort reality, neuroses leave physical, psychological and social reality intact. According to Freud, neuroses reflect poorly resolved unconscious emotional conflicts, which lead to psychological defense mechanisms that attempt to protect the person from consciously experiencing these conflicts but result in the observed behavioral and psychological symptoms.
  
  Neurosis takes many different forms, including
  
  
  anxiety disorders: excessive severe worrying.
  phobias: abnormally intense fears with no objective cause.
  obsessive-compulsive disorders: repetitive acts, such as repeatedly checking whether doors are locked, oven is turned off, etc.;
  repetitive handwashing and intense concern about "germs," etc.
  hysterical disorder (not the everyday meaning of intense over-excitement), such as: conversion disorder: psychological problem
  showing up as a "physical" disorder that cannot be result from
  physical pathology (e.g., "glove anesthesia" is apparent lack of pain
  perception from the hand, which cannot happen as a result of damage to
  the nervous system). dissociation disorders: multiple personalities
  (real cases are much rarer than the "celebrety cases" that reflect the
  intense interest people have in this peculiar condition);
  depersonalization in which a person no longer feels "real" and feels
  that his/her experiences are not real, to the point of feeling an arm
  or a leg is abnormally small or not even a part of one's own body.
  Factitious disorders: physical symptoms, such as dizziness, rash,
  vomiting, fever, etc., and psychological symptoms, such as
  hallucinations and memory loss, that turn out to be under the
  sufferer's control.
  


Note that the term neurosis has fallen out of favor, and that the subtypes mentioned above are taking hold. In general, Freudian analysis has lost its hold on in psychiatry. Now neurosis is divided into finer pieces, like panic disorder, social anxiety and obsessive-compulsive disorder (source: NY Times)