When we talk about "hero", we are talking about the main player who played the hand. If you show a hands history to a friend, a hand saved on your computer, when you replay the hand with your tracker, you will be named as the "hero" of the hand. All of your opponents will be named as the "bad guy". When you call a hero, you put yourself in the shoes of 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 French and English as well as in other languages.
Hero vs naughty
Using the right vocabulary makes it easier to understand each other. Sometimes you want to analyze a hand by chatting with a friend or with players on poker forums. You might ask yourself, "Was it a good bluff from hero" or "If you were a bad bluff, would you have made the call? It should be seen in the same way as when analyzing a literary work where there are heros (e.g. Batman) and villains (e.g. the Joker).