Poker players can be divided into groups:
Will win a couple of hands by bullying opponents with great bets, but has no real chance of leaving the table with a profit. He just keeps betting relentlessly until he loses everything. When playing this kind of “opponent“, you have to wait for a decent hand and call his all-in. It requires a great deal of patience and a bit of luck.
Plays a lot of games even with weaker hands, is able to bully his opponents. However, only experienced players, who are good at evaluating their opponents, can profitably play this way. If you are still a beginner at poker, don't try this game style or try it out for play money at first. There is only a small difference between an agressive player and a maniac.
Keeps waiting for decent hands, bets only when holding a strong hand and plays it aggressively. He usually doesn't have to fear losing, as his hand is likely to be the winning hand.