A bond is a line drawn from your character to something they are not free of. It names the other end — a person, a place, a debt — and it says what the tie costs you when it pulls.
Making a bond
You write bonds at creation and you gain them in play, usually without meaning to. A bond needs two things: the other end, and a verb. "Marrin, who I left" is a bond. "Marrin" is a note.
When a bond pulls
A bond is inert until the story puts it under load. When it does, you choose: honour it and take the easier path through the scene, or refuse it and mark the refusal. Refusals accumulate, and a bond refused enough times stops being a bond and becomes something colder.