"A man stands in front of the house, but he is not familiar."
Translation:Egy férfi áll a ház előtt, de nem ismerős.
De just means "but". There isn't a lot of discussion needed. :)
But to make it a bit more complete, de is a non-restrictive "but" and it's not exchangeable with hanem. Hanem is only used is constructions of "nem [x], hanem [y]", saying that [x] does not apply, but instead [y] does.
De is used for all other instances of "but".