This is an excerpt from Complete Soccer Goalkeeper by Timothy Mulqueen & Michael Woitalla.
Punt: Height and Distance
Punting involves striking the ball in the air after dropping it from the hands (figure 6.1). This type of kick enables the keeper to send the ball a long distance upfield and with height.
Keepers should swing through the ball and land on their performing (kicking) foot. The punt is not as accurate as the drop kick or sidewinder. In fact, the punt often results in a 50-50 ball. A punt may even give an edge to the opponent's players because they are facing the ball and can run into it, sending it back the way it came.
The punt is used when a keeper wants to buy time for his team and gain some territory, especially if his team has been under pressure. Keepers also use this technique if the surface that they are playing on does not allow for a safe drop kick.
Drop Kick: Speed and Accuracy
The drop kick is a half-volley strike. The keeper drops the ball from his hands and makes contact with his foot after the ball has taken a quick, short bounce off the ground (figure 6.2). The drop kick is a more accurate way for the keeper to advance the ball up the field than the punt.