The Relationship reading treats a couple as a system: you, your partner, the bond between you and the outlook, each in its own position. It suits any relationship that actually exists — including the undefined kind — where you need to see what is really going on.
It doesn't work for one-sided stories: if the person doesn't know how you feel, the "bond" position comes out empty. The Feelings reading is the accurate one there. And it doesn't answer "is he cheating" — suspicion needs a different instrument, and usually a conversation.

