It is a defining geographical feature of Croatia and as such had an immense influence on the shaping the history (and present) of Croatia. Plus it is amazingly beautiful.

No, Croatia has only about 4,7 million citizens, and about 8 million Croats living around the globe. (turbulent history)

Croatia is probably most famous for its beautiful coastline and many islands, among other things

lots fo things. croatian history lasts from the 7th century.

but the main parts are probably that the shape of Croatia changed a lot and Croatia was often in someone else's property (the Turks, Austria-Hungary)

Marcus Tanner has written:

'Croatia' -- subject(s): History