Piles or hemorrhoids are swollen and inflamed blood vessels in your back passage.

It is usually a gradually progressive disease and one of the most common cause of bleeding while passing stools.

Hemorrhoids or Piles can be
Internal: Internal hemorrhoids develop within the anus or rectum
External: these develop just outside the anal opening

Internal piles can prolapse as the disease progress. They can be classified into 4 grades:
Grade 1: prominent vessels but no prolapse
Grade 2: hemorrhoids prolapse while passing stools but reduces spontaneously
Grade 3: hemorrhoids prolapse but can be reduced by manually
Grade 4: permanently prolapsed hemorrhoids