Tactical play covers such a wide area that it is hard to define it exactly. It's like pornography; hard to define, but you know it when you see it.
Many amateurs like to think they have a tactical style and, having heard the saying “chess is 99 percent tactics,” think that by playing tactical chess they are bound to win more games. What exactly is meant by tactics? Most players can't come up with an adequate description of what a tactical style is and from what I've seen online, some consider blundering away a piece to be sacrificing it. According to Wikipedia, a blunder is a very bad move usually caused by a tactical oversight. Especially among amateur and novice players, blunders often occur because of a faulty thought process where they do not consider the opponent's forcing moves.
Was Paul Morphy a strategist or a tactician? Morphy's play was revolutionary for his era and his combinations were amazing, but what made all those fantastic tactics we see in his games possible? His play in the openings emphasized positional development which lead to advantages that allowed him to dominate the position and often finish off the game with a brilliant attack.
And what of Alekhine? Spielmann observed that he could see combinations as well as Alekhine, but he just couldn't get the positions Alekhine got. Why? Alekhine knew how to build up overwhelming positions.
There's more to tactics than just willy-nilly sacrificing something. So, what is a combination or tactic? The Encyclopedia of Chess Middlegames gives the following tactics categories:
Double Attack
Pawn Breakthroughs
Blockades
Decoys
Discovered Attacks
Passed Pawns
X-ray Attacks
Interception
Deflection
Pins
Demolition of Pawns
Overloading
Annihilation of Defense
Perpetual Attack
Intermediate Move
Space
Clearance
That's a long list of motifs one has to be able to recognize if one is going to adapt a successful tactical style. Even if one prefers to play in a strategic style, you still have to be able to recognize all that stuff to avoid making a tactical blunder yourself or to take advantage of one by your opponent.
`According to Wikipedia, a combination is a sequence of moves, often initiated by a sacrifice, which leaves the opponent few options and results in tangible gain.
Combinations are sufficiently forcing that one can calculate exactly how the advantage will be achieved against any defense. Indeed, it is usually necessary to see several moves ahead in exact detail before launching a combination, or else the initial sacrifice would not be undertaken.
Describing exactly what constitutes tactical play isn't easy though as seen by the definitions of some of the greats:
Emanuel Lasker: A variation which leads to a desirable issue by force.
Znosko-Borovsky: A maneuver distinguished by surprise (usually springing from a sacrifice) which brings about a sudden change in the position, and should gain some advantage.
Euwe: A short part of the game within which a certain purpose is attained by force.
Fine: A double attack.
Botvinnik (a forced variation with sacrifice) disagreed with...
Romanovsky’s definition (a variation in the course of which both sides make forced moves and which ends with an objective advantage for the active side) because in Botvinnik's opinion it would include things which come under the category of maneuvers. Botvinnik’s definition covers most combinations, but not all according to CJS Purdy.
For example, consider a Queen in enemy territory that doesn't have an escape route. A series of threats that have to be met by the “threatened” side ends up with his losing the trapped Queen, but there may not have been any sacrifice at all. Purdy said tactics are characterized by violent moves, but not necessarily sacrifices.
In some positions there is a winning tactic and either the player finds it and wins, or doesn’t and the game goes on, but in most positions there are no tactics at all. And, here's the point many amateurs fail to understand, spectacular, forcing moves may be unsound because nothing can be forced and the opponent has a wide choice. That approach may work for a strong player like Tahl or Nezhmetdinov, but for most of us, entering such positions also means we have just as good a chance of blundering away the game as our opponents!
The trick is to find a move that will give the best results no matter what the opponent does. That is position play; it deals with small improvements in a position and you are not likely to get the chance for a combination unless you can build up an advantage in little ways like Morphy and Alekhine did. Obviously, a sound tactic trumps all positional considerations whenever it comes up, so you have to be on the lookout for tactics at every move.
Purdy recommended that when (if) you see an opponent’s threat try to imagine that he could not execute it and examine possible attacking moves because one of them could render the threat harmless. The danger is that when you see an opponent's threat, the natural reaction is to start looking for a defense and suddenly find yourself just reacting to your opponent's moves. On the other hand, if you don’t ask yourself if he has any threats, you will constantly be making blunders.
It's also necessary to realize that a positional advantage is not always necessary to be able to pull off a tactical coup. It is true that tactics are usually brought off by the player with the superior position, but many tactics arise when the stronger side misses something. We've all blundered in won positions! Never be deterred by what appears to be a positional disadvantage. Every part of the board must be examined for some accidental feature that may give rise to a combination. That means you have to be able to recognize all those 16 motifs The Encyclopedia of Chess Middlegames sets out when you see them. So, there's more to playing tactical chess than just sacrificing something.