Since several years, all Apple mouses have one unique button (the mouse goes down like one unique block), but the mouse it is able to detect which finger is pushing the mouse down, so it detects a right click or a left click.
The idea was people coming from PCs would be able to use the mouse as usual (just enabling this behavior in the preferences of OS X), or all time Mac users could still use their mouse like always...
Until this last Magic Mouse, the one tha it is also a touchpad, I have never been a fan of Apple mouses, for me they were always the worst anatomically mouse design in the market... But I have to confess that the touch features of this last mouse make me go more quick in some tasks... I don't like also their keyboards, they are way better than 99% of the market, but I brought a mechanical keyboard... Much better writing experience...