The phrase "unknown territory" means a place or situation that is unfamiliar, where we don't have much knowledge or experience. It refers to stepping into something new or uncertain. Full definition
Not only that, this was new coastline for us to explore in unknown territory. (ordinarytraveler.com)
While it may be unknown territory for newcomers, current residents already know the secret of its appeal. (creditdonkey.com)
These questions are going to have to be answered in novel litigation and by courts exploring unknown territory, and the earliest previews of these issues only confirm that fact. (momentum.law)