Overview
A strategy strongly dominates antoher strategy if the payoff in the dominating strategy for every state of the game is greater than the payoff in the strategy that it dominates. A strategy weakly dominates another strategy when its payoffs are greater than or equal to the payoff in the dominated strategy.
When a strategy is dominated by another strategy, then that strategy can be eliminated from consideration, because there is no reason to choose the dominated strategy over the dominating strategy.