There are two aspects to custody:
First, there is legal custody, which is the decision making power regarding the child (ren). If the parties have joint custody, major decisions must be made by both of the parties together, but minor decisions may still be made by the one parent who has care of the child (ren) at the time that a given issue may arise.
Joint custody works well in situations where there is good communication between the spouses and they are able to focus on what is in the best interests of the child (ren). If the parents have too many disagreements, joint custody can be more challenging.
The second aspect of custody is physical custody. Physical custody deals with the time that each parent will spend with the child (ren).