Physical custody is what it sounds like: the parent with whom the child resides. This arrangement means that the child's legal residence is with the parent whom the court has granted physical custody. It also means that the custodial parent has the responsibility to care for the child's immediate day-to-day needs, such as food, clothing, shelter, and entertainment.
Courts may grant sole or joint physical custody. In sole custody situations, the non-custodial parent is entitled to visitation rights, which can be worked out between the parties or set by the judge based on the best interests of the child. In a joint custody arrangement, the parents divide their time with the child more-or-less equally.
After the judge signs off on an agreement or rules on the merits, the custody arrangement is final unless there is a finding that a change in circumstances affecting the best interests of the child warrants a modification of the custody order. All custody orders automatically expire when the child turns 18 (can be extended to age 19 or graduation from high school, whichever comes first).