How does hasMany and hasOne work in Grails?

I am having problems defining one-to-one and one-to-many relationships with domain classes. I have the following domain classes

class Team {
    static hasMany = [players: Player]
    static hasOne = [coach: Coach]
}

class Person {
    String name
}

class Player extends Person {
}

class Coach extends Person {
}

      

        
        
        
      

    

So my questions are:

1- Do I need to declare a variable team

in the player and in the trainer?

2- Do I also need to announce belongsTo

?

3. Given the above classes, is it preferable to use hasOne?

Thank.