I like my definitions to be as accurate as possible:
Weak Anthropic Principle(WAP): "The fact of our location in the Universe is necessarily privileged to the extent of being compatible with our existence as observers."
Strong Anthropic Principle (SAP): "The Universe (and hence the fundamental parameter on which it depends) must be such as to admit the creation of observers within it at some stage."
(see Brandon Carter, "Large number of coincidences and the Anthropic principle in cosmology", 1974. Later this was elaborated with additional anthropic principles of similar flavor by Barrow and Tipler, 1986).
Given the above definition, the WAP says in effect that the reason why earth is so hospital to intelligent life is because we grew up here (to use a Carl Sagan metaphor). The SAP says that the reason why we observe some unique physical constants is that the universe with those parameters must be able to admit life so that we could be here to notice these unique variables. WAP reduces to possibility of constant values, and SAP reduces to possibility of life given certain constant values.
What the SAP does not say is why those values are such as they are to yield life (a common misinterpretation is to suppose that SAP requires intelligent design). SAP could be interpreted within an ensemble universe cosmology where all sorts of values are possible, but only universes with select constant values can support life. It does not necessarily imply intelligent design.
>>>It says that Buriden's Language Removed need not choose one hay stack over the other. The universe could have simultaneously chosen hay stack A (exist) and hay stack B (not exist)... and us organisms simply emerged in the universe that choose hay stack A (of course). This way there is no symetry breaking, and anthropic principle is powerful argument (actualy in Alex's favor). No symmetry breaking here... both possibilities were chosen. Life just took better to a universe that actualy exists.