Tactics is how you win a battle.
Strategy is how you win a war.
Grand Strategy is how you implement what you want after the war is over.
These terms can have other meanings but I like the idea that Grand Strategy could also mean an overall approach to life, a bigger aim, a super long term goal, a reason for being; anything in fact that is one's real and perhaps even embarrassing motivation. Or lack of it. Lots of people have 'being confused' as their grand strategy.