Simply put, joint custody means that both parents share equal input and/or spend equal amount of time with the child/children. Sole custody is essentially the opposite - when only one parent has the decision making power and the child or children live almost all of the time with that one parent. Custody is actually broken into two categories (physical and legal) and then labeled joint or sole within each category. Physical custody describes where a child lives most of the time and what parent will have visitation, whereas legal custody describes access to records and major decisions such as to schooling, religion, extracurricular activities and non-emergency health procedures.
It is most common to see joint custody in the category of legal custody. Joint legal custody means that both parents have input and should be involved in major decisions. Per O.C.G.A. § 19-9-1,(Georgia parenting plan law) there must be a designated tiebreaker or final decision maker if the parties cannot agree (usually the primary physical custodian). This prevents the parties from needing the Court's intervention every time there is no agreement on any one issue.
In the category of physical custody, the parties must designate a primary physical custodian and typically do not label physical custody under the "sole vs. joint" designation. The primary physical custodian is the person the child/children live with most of the time and the noncustodial parent has visitation or parenting time. According to O.C.G.A. § 19-6-15 (Georgia child support law), even if the parties share equal amount of time with the child/children, the Court must still designate a primary custodian.