It can be any animal, human or thing you want it to be. When you start getting answers, you can draw a character web, like this example. Put your main character's name in the circle in the middle, and all of his or her characteristics on the lines coming out of the circle. Draw a picture of your main character. That will help you visualize what he or she is like.
Every story needs to take place somewhere.
Well, duh, you might say. But your story's setting can have either a big or little impact on the story. Just a story about a girl and a dog in dusty old Kansas, that's what. The challenge your character must face and overcome Without a problem, your story would be dull as watching paint dry. But when you give your main character a problem to solve, your story comes alive.