Tactics and Strategy, as they relate to board games, will vary based on the specific game-play dynamics of each specific game. And in many games, the limited scope of either the board itself, or of the possible choices available to players, will exclude "tactics" from being applicable terminology for that particular game.
Having said that, for games that have enough scope to include both Strategy and Tactics, I would definitely consider them very separate, and this is what I believe the difference is:
Strategy: All games have starting positions, and all games, by definition, have winning conditions. Strategy starts out as "the player's intended course to follow between those two points, starting and winning"(first I'll go from A to B, then to C, then D, E, F, G ... then win). After the game starts, Strategy evolves continuously throughout the game to be "the the player's intended course to follow between the current state of the game and winning" (I've made it to C, but I can't get to D, I'll go to H instead and then back to E from there, and then F, G ... win).
Tactics: Tactics are specific plans, maneuvers, plays, adjustments, etc., taken through the game, in reaction to the current state of the game, and which are intended to either keep the player on their currently desired strategic course (make move A, not move B, because that will get me closer to C which is where I want to be), or get them back on that course if they have been forced off of it (make move B, because move A isn't available any more, but I can still get to C from there), or to get them on to a new strategic course if the intended course has changed from what it was previously (make move B because I no longer want to get to C. Since A isn't available like I'd hoped, I'm going for D instead).
defining overall objectives that will lead to victory,
the means used to gain those objectives).