When we say "hero", we mean the main player who played the hand. If you show a hand history to a friend, a hand saved on your computer, when you play the hand back with your tracker, you will be called the "hero" of the hand. All of your opponents will be named "villain". When we talk about a hero, we are talking about the player who has to make a decision. On a replayer, the hero will be the player whose cards are known. This is a very common vocabulary among poker players, both in English and in other languages.
Hero vs. villain
Using the right vocabulary makes it easier to understand each other. Sometimes you want to analyze a hand when talking to a friend or players on the poker forums. We may then ask "was it a good bluff by hero?" or "if you were naughty, would you have made the call?" You have to look at it the same way as when you analyze a work of literature where there are heroes (e.g. Batman) and villains (e.g. the Joker).