Seantor's right - we'll ignore the fact that neither of these hands are played unusually aggressively (the first hand is totally passive post-flop) and the fact that with AKs and KK how the hell else are you going to play the hands, and we'll concentrate on what aggression means.

It means being the person to force the other person to make decisions about their stack. It is asking questions of them that they can only answer if they have good cards or big balls. It is nesuring they never get free cards or good odds when they're drawing; it's re-raising when they claim to have a hand to see whether they're really prepared to take it all the way. It can involve bluffing, but you can't just make raises and re-raises and expect to make players fold; you need to target players accurately, identify weakness, take advantage of position.

You also need to be able to fold. Since aggression will usually accompany non-nut hands, you need to be prepared to lay down, after investing a sizeable amount of chips, when their response is to fire back hard.