To separate rough sleeping (sleeping outside) from homelessness (not having a home).

Someone who has no official address, but is sleeping on the floor in a friend’s house temporarily is homeless but not rough sleeping.

Someone who has a home and address, but isn’t able to go there for some reason (often escaping from domestic violence) may end up “sleeping rough” i.e. outside on a bench, in a tent or shop doorway.

Many other variations/examples obviously, and plenty of cases of both together.

Both situations need slightly different support.