Whoever is a word that refers to a person whose identity isn't known or isn't important in the situation.
When we use whoever, we often talk about situations where it doesn't matter who did something or who gets to do something. For example, let's say you're planning a party and one of your friends wants to know if they can bring their friend. You might say, "Whoever brings the most music to play is welcome to stay longer." In this case, whoever means any person who meets that condition - it doesn't matter which specific person. It's like saying, "Anyone who does that gets a prize!" Whoever is used in sentences where we don't care about the identity of the person involved.
(interrogative) Who ever: an emphatic form of who.
Example: Whoever thought up that stupid idea?
