what is difference between "free access" and "open access"?

I wrote following text to complete Mr Zerehsaz's posts.

There seems to be a general misunderstanding that the aim of the Open Access movement is to make the scientific research literature free online. But there is a difference between "free access" and "open access".
This distinction was part of what motivated the Bethesda definition of Open Access Principles that we published in the first issue of Open Access Now (July 14, 2003). That definition clearly states that access to the information should be free, but in addition the work should be open to re-use and redistribution, and that it should be deposited immediately upon publication in a public online repository (such as Pub Med Central).
Publishers who offer free online access on their own websites still have a long way to go before their research articles can be considered Open Access. The benefits and promise of Open Access will only be realized when this distinction is clear in the minds of authors and publishers. Only then can the literature move from being ‘free’ to being truly ‘open’.