Joint custody is where two parents share joint decision-making for the child, usually for major life decisions. For the everyday decisions affecting the child, usually the parent who is in possession of the child makes those decisions, but when a major life decision affects the child, such as surgery, education or religion, parents who are joint custodians must agree on those decisions.
Sole custody is where one parent is granted custody of the children and will be the sole decision maker for the children. They will decide where they live, what doctor to see, what school to attend, etc.