I find that most people do not know the difference. To explain in simple terms, a disease is an unprovoked pathological process. A disorder is a provoked one. Your vein issues are a disease. It came from natural wear and tear on your veins. Usually from standing long hours, exercise, and, in women, childbirth. You did nothing wrong to acquire these issues. Imagine that vein disease is like grey hair and wrinkles. Nothing you did wrong, everything you did right.