In tennis, there are a variety of types of shots (ways of hitting the ball) which can be categorized in various ways. The serve is the opening shot of a point, and it's typically struck using an overhead throwing motion. Shots struck during the point are categorized into two major categories: groundstrokes, which are hit after the ball has bounced, and volleys, which are hit out of the air. Both groundstrokes and volleys can be further classified as either forehands or backhands, with the classification determined by the side of the body on which the ball is hit.
Certain kinds of groundstrokes and volleys have specific names, so that tennis players can better communicate about the points they play. A lob is a groundstroke hit very high in the air, typically with the intention of hitting over the head of an opponent who is positioned at the net. A passing shot is a groundstroke that is driven past an opponent at net. A smash (also referred to as an "overhead") is an overhead swing used to hit high, floating balls with high velocity. It utilizes a similar motion to the serve. A drop shot is a shot a slow moving shot, typically played with backspin, that is intentionally hit short, in hopes the ball will double bounce before the striker's opponent can retrieve it.
Shots are often further classified by their direction. A cross-court shot is a shot hit from the left (or right) side of one player's court to the left (or right) side of the other player's court (from each player's own point of view), so that it crosses the lengthwise centerline of the court. A down-the-line shot is one that is hit more or less parallel to, and near to, one of the sidelines, so that it never crosses the centerline.
Shots hit during a point without the ball having bounced are called volleys, while shots hit just a split second after the ball bounces are called half volleys.
A slice is a groundstroke or volley hit with backspin, while a topspin shot is a groundstroke or occasionally a volley hit with topspin.
Thus tennis shots can be categorized according to when they are hit (serve, groundstroke, volley, half volley), how they are hit (smash, forehand, backhand, flat, side spin, block, slice, topspin shot), or where they are hit (lob, passing shot, dropshot, cross-court shot, down-the-line shot).
All shots that pass either over or around the net and land anywhere within the confines of the court, lines included (except for serves, which need to land inside the designated service box), are considered good. Shots that touch the net and then land in their designated area are also considered good, with the exception of serves. Serves that fall into the service box after touching the net are called service lets, and the server simply serves again, without any impact on the scoring.