What are handicap bets?
If one competitor is clearly favoured over the other, bookmakers will often allow the weaker competitor a "head start", which is taken into account when calculating the final result. For example: Bayern Munich vs. MSV Duisburg. Handicap 0-2 (Duisburg is allowed a 2-goal head start). Even if Bayern really wins 1-0; you still win if you placed a handicap bet on Duisburg because the handicap makes the score 1-2 for the purposes of the bet.
You place a 0-3 handicap bet on the game Germany vs. North Ireland. The final score was 2-0. When the handicap is factored in, the following score results:
0-3 + 2-0 = 2-3
Your “score” (the score that counts for the purposes of your bet) is therefore 2-3. So, if you bet on North Ireland in that game, you win.