Asian handicap is basically giving the other team the lead.
If Man Utd v City is -1, then for the purposes of betting, City start off the match with a one goal lead. You then bet however much you want on either Man Utd or City. If Man Utd win by 2, you win your stake; if they win by 1, you win nothing; if they draw, you lose.
If the handicap is -0.5, then if Man Utd win by 1, you win; if they draw, you lose. It eliminates the draws.
Your specific example is placing half your stake on team A at -1.5, and half on team at -2. If team A wins 2-0, you win half of what you bet.