Visa's/Passport stamps?

Question

What is the difference between these?

Answer 1

example i visit  HK   monthly  US passport   the HK  border police  just stamps  my passport   with ared stamp and they enter  the days of validity   range from 7  to 14 days  while i live in china  i have one page in my passport  with a reg Chinese visa issued and glued to one page

Answer 2

Visas denote permission to enter a country for some particular purpose. Passport stamps can serve as temporary visas, depending on the country and the nationality of the traveller, however, most of the time they simply show entries and exits.

Answer 3

Passport stamps are temporary visa's.  They expire after a certain amount of time.