The Guardianship Act gives guardianship to both natural parents in a marriage and unless a court orders otherwise, that is also the case after divorce. Guardianship is essentially parental authority and would include, for example, representing them in Court and looking after their financial and legal affairs.
A sole guardian of a child is rare - but such person has a lot of power - such as allowing a child to get married with out asking the other parent, or more importantly, via a will, appointing a person to succeed them as sole guardian.
Custody is the parental control and supervision of all the activities of a child's day to day life. It would include guiding the child in religious activities - or preventing them from having certain friends. Custody is understandably the cause of much anguish in divorce proceedings and the subject of some intense debates and legal cases. Our courts recognize these days that either parent can in fact make a better custodian and it is not automatic, for example, that custody is awarded to the mother. A court may award sole custody to one parent or joint custody to both parents.
Access allows a parent who does not have custody to see his or her child and enjoy their time together. In reality it is a right given to a child, although most people do not realize this, to see both his or her parents, as this is generally in their best interests.