This subgenre is, more or less, the inversion of the alien invasion genre. Or, to quote the old saw, the other side of literature, because “A man goes on a journey…” and “A stranger comes to town…” are the same story from flipped POV.
Depending on your theme and story, your exploration can be quiet and gentle, or it can be loud. Star Trek: The Next Generation (far more than the original show) emphasized the Prime Directive in ways that explorers and sociologists slipped in quietly to learn about any given culture, hopefully without revealing themselves and