PURPOSE OF UCCJEA. The purpose of the UCCJEA is to reduce disputes between the states regarding which state has the ability to make a decision regarding a child's custody, welfare etc. In the past courts would each make a different decision about a child and then argue about which order is controlling or which state should have made a decision. These arguments still occur but generally there are less of them because the UCCJEA is the law in each state and the UCCJEA has a system of deciding which state should make that child custody decision.
SIX MONTHS. If you do not have a custody order then the general idea is that the court of the state that the children have lived in for the last 6 months is their 'home state,' there are some exceptions. Also if there is a custody order it could be modified by a new state if the minor children and parents are not in the state that made the last custody order. This is highly complicated but can be explained by an attorney.
JURISDICTION. According to Black's Law Dictionary "A court's power to decide a case or issue a decree." In the context of child custody it is the court's power to make an initial custody order or to modify a previous custody order.
INCONVENIENT FORUM. Even if there is jurisdiction a court can decide that it would be better for the case to be decided in another state and therefore transferred to that state if certain conditions apply such as, where the evidence and witnesses are. This is a separate decision from jurisdiction and the UCCJEA states which court can make that decision.
CHILD SUPPORT IS SEPARATE. Oddly enough the state where the payor resides can have jurisdiction over child support while a different state has jurisdiction over custody.
In conclusion the Uniform Child Custody Jurisdiction and Enforcement Act has some provisions which are important to know whether or not you are looking for a modification or a custody order, if you and your child or you and the other parent live in different states you can be dragged into court in that other state. You should know under what circumstances you can be dragged into court in that other state and if you wish to prevent it you might have to request a custody order in your state before the other parent does in their state.