Strategy vs. Tactics : difference?

Tactics are like sacrificing a piece or finding a fork, strategy is like bringing more pieces into the attack or playing a more postional move

Thanks And what shall I learn/focus as a beginner

Tactics: short term and concrete moves.
Strategy: long term and more abstract.

Tactics is more calculation, a sequence, fork, skewer, double attack, sacrifices.

Stategy is more analysis, pawn structure, prophylaxis, look for weakness, develop a plan, improving pieces, positional chess.

Tactics is short term.
Strategy is long term.

You should focus on tactics first.
'Chess is 99% tactics' - Teichmann

A strategy or plan is the precursor of a tactic. It doesn't do much good to to focus on learning strategy if you are unskilled at tactics, which are, after all, the point, the end result, of successfully executing a strategy / plan....

Improving Your Chess - Resources for Beginners and Beyond.....

https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond

Good Positional Chess, Planning & Strategy Books for Beginners and Beyond...

https://www.chess.com/blog/RussBell/introduction-to-positional-chess-planning-strategy

All players, at all levels, should study both tactics and strategy. However for players rated below about 1400 Elo the primary focus should be developing proficiency in tactics.

Tactics is short-term and strategy is long-term. Both work together to achieve overall success.

Strategy is your plan; tactics are how you implement that plan.

Seen a great quote about this, "Tactics is knowing what to do when there is something to do, strategy is knowing what to do when there is nothing to do"