European handicap betting gives one side a whole-goal head start or deficit before kick-off, then prices the adjusted result as a normal three-way market: home, adjusted draw, away. Back Arsenal −1 and they must win by two or more; a one-goal win lands exactly on the adjusted draw and your bet loses.
That last point is the trap for newcomers and the whole difference from the Asian version: European handicaps have no refunds. The third outcome (the adjusted draw) is a real, priced possibility that beats both sides of the handicap, which is why the odds look more generous than Asian lines on the same match.
Arsenal −1 at 2.60 against Fulham. Arsenal win 2–0: bet wins. Arsenal win 2–1: the −1 makes it 1–1 — the adjusted draw wins and your bet loses, where an Asian −1 would have refunded the stake.