someone, anyone please explain this hand to me

Party Poker 2/4 Hold'em (6 handed) FTR converter on zerodivide.cx

Preflop: Hero is Button with Ac, 8s.
UTG raises, 1 fold, CO calls, 3 folds.

Flop: (5.50 SB) Kc, 4d, 7d (2 players)
UTG bets, CO calls.

Turn: (3.75 BB) Js (2 players)
UTG bets, CO calls.

River: (5.75 BB) 2d (2 players)
UTG bets, CO raises, UTG 3-bets, CO caps, UTG calls.

Final Pot: 13.75 BB

Results in white below:
UTG has Ah 5s (high card, ace).
CO has 6d Ad (flush, ace high).
Outcome: CO wins 13.75 BB.