In Game Theory: A “strategy” for a player in a game is a “complete specification of what that player will do in all the circumstances they find themselves in”. Easy to say, sometimes not so easy to do – ie identify in a complex game or describe in words.
In some games “lists” are a convenient method of identifying strategies, as explained in this simple 2 person game example. It works well here – so try it in the 3 person “Garden Contributions sequential game” from Dixit , Skeath and Riley pp 61. You’ll quickly understand why the shorthand “list” way of describing a strategy is much superior to say trying to write down all of the logically possible strategies via a combination (conjunction) of “if….then…” statements. But in more complex games writing down discrete lists can be both tedious and confusing.