If you don't know what a slice is, you are not alone. Many beginners are unsure of what a slice is. Once you master the golf swing basics, you will want to focus on other aspects of the game. One of the most common problems is the slice.
A slice is when there is a significant tilt of the spin axis. The ball will go in a clockwise spin to the right (opposite for a lefty). The slice causes the ball to end up to the right of your expected target. A fade is the same thing only less extreme.
What causes a slice?
Stance - Your stance may be too open.
Grip - Your grip may be open or weak.
Backswing - Your backswing may be too upright.
Downswing - Your downswing may be flaring open the clubface.
Often all of these in combination can be the cause of your slice. However it could be as simple as your grip alone. Your grip should be loose, but not too much so. You want to hold on tight enough that you won't lose the club when you swing, but not too tight to where it impedes with your control.
Learning and mastering the golf swing basics can help you cure your slice. Books are a great place to learn the basics. You will find that books often go into much greater detail and depth than a teaching pro will. It is easy for a teacher to miss or forget to go over some steps.