Fantastic Facebook games and where to find them?

So I have heard that there is something called Facebook games. I have never tried that before and am a little curious. Can anyone recomend any of them and how do I access them? I am using an iPhone SE and an iPad Pro 9.7.

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Mafia wars

The only one I am aware of is Mafia Wars but I don’t know how to play these games in iOs. Do I need to use Safari or can I do it in the Facebook app?