New - question on performance

Making a first person survival horror game. It’s pretty simple, comparable to “Slender: The Eight Pages” sort of thing.

The game is going to feature a large house with furniture and whatnot, as well as an outdoor area.

How does the engine render things? If the polygons of the furniture are not in the players sight, will they still contribute to overall performance? Same with the trees outside while the player is inside?