Isn't strategy the over-all plan and tactics the maneuvering of pieces to achieve that plan? For example, the strategy of White playing against some defenses as the Sicilian might be to keep Black bottled-up and allow White to develop better.
Strategy
"Strategy" is a nebulous term and the more you learn about it the harder it seems to be to define (at least for me).
An "over-all plan" can be strategic, and that's certainly part of strategy. But a plan can also be a forcing tactical sequence that results in an advantage, and in that case it's not strategy it's tactics.
I like Paul's definition and have used it myself: if you need words to describe what you're doing, it's strategy, else it's tactics. But that doesn't do much in terms of saying what strategy in and of itself.
I think another way of looking at it is that strategy is the statistical trends of centuries of play distilled into an idea on a chess board without a concrete purpose.
We put rooks on open files when there's no tactical sequence to pursue, for example, because over the centuries it has become clear that rooks have a strong statistical tendency to be useful on open files eventually. So in lieu of something better, putting a rook on an open file is statistically likely to be a good move.
By contrast, if there's a concrete reason for the rook to be on an open file such as a forced sequence of moves that leads to getting doubled rooks on the 7th, then it can't really be said to be a purely strategic move.
And here we see the problem that lies at the heart of trying to define strategy, very often a move may be made for strategic reasons but end up serving an immediate tactical end. Consider if you don't notice the forcing sequence leading to the doubled rooks on the 7th until the move after you placed the rook on the open file because you didn't know what else to do? When you annotate the game where do you say the forcing tactical sequence started, since the rook to the open file is part of the tactical sequence you can't say it starts the next move. By the same token, it's disingenuous to say you played the move with the tactic in mind.
What exactly is ment by stategy. If I have a plan, is that stategy?