Custody ultimately has to do with decision making abilities over your child. For example, the parent who has custody over their child is the one who has the power and authority to make important decisions about the child, such as medical, educational and religious instruction. The child may not necessarily be residing full time with the custodial parent. Parents who have joint-custody make decisions together. With joint custody, parents make the important decisions together/jointly regarding the welfare of the child – they share it. For joint custody to work, parents have to be able to communicate with each other and to co-operate with each other even though they are not living together and no longer in a relationship. Please note that there can be many variations of custody and joint-custody as well, depending on what the parties agree on. For example, there could be a clause in an agreement that provides for joint decision making over a child but in the case of a disagreement, one parent has the final say; however, if the opposing party is not happy s/he has the option to bring the matter before a mediator or a family court within a certain time frame.