At its most basic, strike means to hit. If you strike someone, you hit them with your hand or a weapon. If lightning strikes, it makes contact. If you strike out on a trip, you're "hitting" the road. If you strike gold, you've "struck it rich"!
Strike can also mean not to hit, as in miss –– as in "three strikes and you're out." That meaning might have evolved from strike meaning to cross off, as in "If you don't come to practice, coach will strike your name from the starting lineup." It might also have led to the idea of a labor strike. If employees want to protest their work conditions, they go on strike, or refuse to work until conditions improve.