In tennis, anytime you hit the ball with the racquet in an effort to get the ball successfully over the net is known as a "shot". There are eight basic shots:
A serve - or, more formally, a "service" - is the tennis shot that starts off a point. You toss the ball into the air and then hit it (generally overhanded) into the diagonally opposite service box.
The forehand is a long tennis shot that, if you're right-handed, starts on the right side of your body, makes contact with the ball and ends on the left side of your body. It's generally hit with a one-handed grip.
A backhand tennis shot is pretty much just the opposite of a backhand. This means that if you're right-handed, your stroke starts on the left side of your body, hits the ball and and ends on the right side of your body. Many players use a two-handed grip, though one-handed grips are also popular. The backhand is considered a bit more difficult to master than the forehand.
A volley tennis shot is made when you hit the ball before it bounces on your side. The opportunity to hit a volley generally arises when you are playing up by the net. It involves a stiff punching motion and aims to hit the ball into an open part of your opponent's court where he is unable to reach it.
A half-volley, like a volley, is also generally hit when you are playing near the net. It's when you hit the ball just after it has bounced on the ground while it's still on the rise.
The overhead smash is a strong tennis shot that often serves as a point-ended (in favor of the smasher, of course!). Often a return to a high lob (see below), it's a shot hit from above your head with a downward serve-like stroke.
If your opponent is far back near his side's baseline, you might want to try for a drop shot. This stategic move involves a gentle tap that gets the ball just over the net where the opponent is unable to run fast enough to return it before it bounces twice.
A lob, a high-hit ball to the back of your opponent's court, can be either an offensive or defensive move. If your opponent is up by the net, you can use the lob to hit the ball over his head and - hopefully - win the point. It becomes a defensive shot when you hit it in order to give you time to get into better position. Be careful, though, as a lob can provide your opponent with the perfect opportunity to come back at you with an overhead smash!