Those are all called 'relative pronouns'. Check this site: https://learnenglish.britishcouncil.org/en/english-grammar/pronouns/relative-pronouns 'What' is a little bit different. It means the same as 'the thing that'. i.e. "I know what you did last summer." = "I know the thing that you did last summer."

Examples: Which person wants it? Who wants it? That is not the right answer. Whose cat is that? To whom are you giving the dog? What is the dog's name?

These words are all VERY different. Did you use a dictionary to look these words up? Research "Relative pronouns" on the Internet.

Which = is used when there is an option of some sort to chose from. "Which" color do I want? "Which" person do I like? Who = is used in reference to a person or people. "Who" is coming with me? "Who" is that person? That = is used when referring to something specific. "That" book. "That" girl. "That" dog. "That" place. Whose = is most commonly used when asking about the owner of something "whose" book is this? "Whose child is this? "Whose" dog is this? It can also be used instead of "who is" Whose coming with me or who is coming with me? In this case its up to you which to use. Whom = its another way to say "who" but I would say it's more proper. What = is a question word "what" are you doing? "What" is that? "What" is this? These are the most usages of these words as your english gets better you will be able to use them more freely. Hope this helps a little!