In
tennis, a backhand is the
stroke, or shot position, that requires the player to hit the ball from their non-
dominant side (i.e., the side
opposite the arm holding the
racquet).
There are two primary styles of the backhand stroke. The first is the one-handed backhand, and the second is the two-handed backhand (made somewhat famous by Chris Evert). The advantage of the one-handed backhand is extended reach and potentially greater power and spin. The disadvantage is somewhat reduced control and accuracy. The two-handed backhand generally allows for faster response and better control, at the expense of some power (This is debatable, and Chris Evert was said to have adopted a two-handed backhand to increase her power by using both arms to effect the stroke). Also, since the use of two hands on the racquet limits the "reach" of the racquet, it forces the player to move further and more precisely to ensure the ball is struck within the optimal strike zone.
Notably, Pete Sampras, one of the best players of all time, (and arguably the best player of all time) began his playing career using a two-handed backhand, and soon moved to a one-handed style because of the advantages of reach and shot flexibility. On the other hand, Andre Agassi, also arguably the best player ever, plays with a two-handed backhand.
In general, the backhand stroke is the weakest for most players, although exceptions to this abound (usually due to a poor or undeveloped forehand stroke).
And as in all human endeavors, there are exceptions to the concept of "backhand" and "forehand." There are players who, for their own reasons, have no backhand stroke, instead shifting the racquet from the left or right hand as needed and hitting a "forehand" from that arm (ambidextrous). And the converse is true, with players who only hit backhands by shifting the racquet, although this is exceedingly rare. Finally, there are players such as Monica Seles who use a two-handed stroke on both sides, nullifying the notion of "backhand vs. forehand".