Here's how I think about it in chess -
tactic: a sequence of moves, almost always short and usually forced with a clear outcome in the short term.
strategy: a sequence of unforced moves designed to create a non-material advantage with no immediately clear outcome.
A tactic is something like pinning a piece and quickly bringing additional pieces to attack that piece in an effort to win a material advantage. The material advantage is an immediate and clear outcome.
A strategy is something like using a pawn structure to gain space. There is no immediately obvious advantage to gaining space, but the added flexibility will often enable (unforseen) material gains later in the match.
