Legal custody of a child means having the right and the obligation to make decisions about a child's upbringing. A parent with legal custody can make decisions about schooling, religion, and medical care, for example. In many states, courts regularly award joint legal custody, which means that the decision making is shared by both parents.
If you share joint legal custody with the other parent and you exclude him or her from the decision-making process, your ex can take you back to court and ask the judge to enforce the custody agreement. You won't get fined or go to jail, but it will probably be embarrassing and cause more friction between the two of you -- which may harm the children. What's more, if you're represented by an Lawyer, it's sure to be expensive.
If you think you have circumstances that make it impossible to share joint legal custody (the other parent won't communicate with you about important matters or is abusive), you can go to court and ask for a change in custody so that you have sole legal custody. But, in many states, you will have to overcome a presumption that joint legal custody is preferable.

Physical Custody

Physical custody means that a parent has the right to have a child live with him or her. Some states will award joint physical custody to both parents when the child spends significant amounts of time with both parents. Where the child lives primarily with one parent and has visitation with the other, generally the parent with whom the child primarily lives will have sole physical custody, with visitation to the other parent. Joint physical custody works best if parents live relatively near to each other, as it lessens the stress on children and allows them to maintain a somewhat normal routine.

Sole Custody

Custody is made up of: legal custody and physical custody. A person with legal custody has the right to make long range plans and decisions for the education, religious training, discipline, non-emergency medical care and other matters of major significance concerning the child's welfare. A person with physical custody has the child living primarily with them and they have the right to make decisions as to the child's everyday needs. Sole Custody is when both legal and physical custody are given to one parent. The child has only one primary residence.
How can I keep custody of my daughter when her father has a criminal record?
One parent can have either sole legal custody or sole physical custody of a child. In most states, courts are moving away from awarding sole custody to one parent and toward enlarging the role a divorced father plays in his children's lives. Even where courts do award sole physical custody , the parties often still share joint legal custody, and the noncustodial parent enjoys a generous visitation schedule. In that situation, the parents would make joint decisions about the child's upbringing, but one parent would be deemed the primary physical caretaker, while the other parent would have visitation rights.
Courts generally won't hesitate to award sole physical custody to one parent if the other parent is deemed unfit -- for example, because of alcohol or drug dependency, a new partner who is unfit, or charges of child abuse or neglect.
It's understandable that there may be animosity between you and your ex-spouse. But it's best not to seek sole custody unless the other parent causes direct harm to the children. Even then, courts may simply allow supervised visitation, while still ordering joint legal custody.

Joint Custody

Parents who don't live together have joint custody (also called shared custody) when they share the decision-making responsibilities for, and/or physical control and custody of, their children. Joint custody can exist if the parents are divorced, separated, or no longer cohabiting, or even if they never lived together. Joint custody may be:

joint legal custody
joint physical custody (where the children spend a significant portion of time with each parent); or

joint legal and physical custody.

It is common for couples who share physical custody to also share legal custody, but not necessarily the other way around.
The court looks very closely at Joint Custody agreements. The most important factor to Joint Legal Custody to Shared Physical Custody is the ability of the parents to talk about and reach joint decisions that affect the child's welfare. If you are constantly fighting over what religion or what school, the court may strike down your agreement.
When parents share joint custody, usually they work out a schedule according to their work requirements and housing arrangements and the children's needs. If the parents cannot agree on a schedule, the court will impose an arrangement. A common pattern is for children to split weeks between each parent's house or apartment. Other joint physical custody arrangements include:

alternating months

years or six-month periods

or spending weekends and holidays with one parent, while spending weekdays with the other.

Joint custody has the advantages of assuring the children continuing contact and involvement with both parents. And it alleviates some of the burdens of parenting for each parent. There are, of course, disadvantages:

Children must be shuttled around.

Parental noncooperation or ill will can have seriously negative effects on children.

Maintaining two homes for the children can be expensive.

If you do have a joint custody arrangement, maintain detailed and organized financial records of your expenses. Keep receipts for groceries, school and after-school activities, clothing, and medical care. At some point your ex may claim she or he has spent more money on the kids than you have, and a judge will appreciate your
Bird's Nest Custody
Bird's nest custody is a joint custody arrangement where the children remain in the family home and the parents take turns moving in and out, spending their out time in separate housing of their own.
The terms "sole custody" and "joint custody" are somewhat generic.
They represent categories of custody, but custody itself is best understood as a continuum, as unique as the parents who divorce.
Imagine a continuum with parents who are completely cooperative at one end and a single parent raising children alone, with no involvement on the part of the other parent, at its other end. At the cooperative extreme, parents may live next door to each other and the children may go back and forth interchangeably. At the other, the non-custodial parent may have died or disappeared. While the former example is more usual than the latter, your family probably falls somewhere in between

Temporary Custody

"De facto" (means "in fact") custody refers to who actually has custody of the child at this time. This can be different from "court ordered custody". In order to formalize custody before you begin litigation, you will need to file for temporary custody. Temporary custody will be based on the "best interests" of the child standard. It is not an "initial" award of custody. Instead it is temporary custody while you wait for the court to hold a hearing.

Split Custody

Split custody is easiest to describe in a situation where there are two children and each parent obtains full physical custody over one child. Some of the considerations that may bring about this result are age of the children and child preference.

Types of Custody

In general, legal custody refers to whether one or both of the parents make legal decisions regarding the child - such as educational, medical or religious choices. A court can give parents joint legal custody, in which case they make such decisions together, or give one parent sole legal custody, in which case that parent makes decisions alone, although the other still has a right to be kept fully informed. Physical custody refers to the child's living arrangements. A court can give both parents physical custody, in which event they share parenting time on an approximately equal basis, or it can give one parent primary physical custody and the other more limited parenting time.

It is possible for a court to award joint legal and joint physical custody to the parents. However, a court can also award joint legal custody, but give one parent primary physical custody. On rare occasions (such as when one parent is mentally impaired but otherwise a positive influence), a court may even award sole legal custody to one parent, with a shared physical custody arrangement.