The binding is what holds the pages together.  Binding methods can include sewing and stapling the inner sheets into outer wraps. However the binding most commonly refers to hardbacks: a book bound in boards covered with material like leather or cloth.  ‘Full binding’, three-quarter, half and quarter binding all refer to leather-bound books.  While full binding refers to a book fully bound in leather, three-quarter binding indicates leather spine and corners covering three-quarters of the top edge (half-binding, only half the top edge, and so on).  When a book is described as a ‘binding copy’ this usually means that it is no better than a reading copy in quality – it either lacks the original binding or a fair/good quality one.