Custody is the right to make important decisions on behalf of the children. Day to day decisions (what to eat for supper) are left to the parent in whose care the children are at the time. 

Irregardless of where the children primarily reside, unless there is an order or agreement otherwise, both parents have joint custody of the children.  They must consult with one another prior to making any major decisions about the children

Where it is in the best interest of the children to have only one decision-maker, the court will order sole custody to one parent.