Hello Nitay
A 6RD host is any host that has an IPv4 address that is translated to an IPv6 address on the network/Internet using IPv6 6RD.
A native IPv6 host is a host on the network/Internet that has an IPv6 address. It is considered to be natively IPv6 because it doesn’t need any kind of translation or tunneling services to function on IPv6.
6RD is considered stateless because packets don’t have to go through the same border or relay router for the feature to function. In other words, there is no single location where the state of the translation for a particular host is saved. Translation can take place over multiple border relay routers.
I hope this diagram also clarifies the above further.
I hope this has been helpful!
Laz