How do SO_REUSEADDR and SO_REUSEPORT differ?

Question

The man pages and programmer documentations for the socket options SO_REUSEADDR and SO_REUSEPORT are different for different operating

Answer 1

Mecki's answer is absolutly perfect, but it's worth adding that FreeBSD also supports SO_REUSEPORT_LB, which mimics Linux' SO_REUSEPORT behaviour - it balances the load; see setsockopt(2)