I see this term very misused in this sub, and I want parents to understand what it means.

There are two parts to custody:

Legal custody is your ability to make legal decisions for your minor child. These are things like what school the kids will go to, if they should have a medical procedure, and even small decisions like if they can go on a field trip. Joint legal custody is standard in divorces. There is no majority vote here, both parents have equal power and if they disagree it goes to court.

Physical custody is when the kids are with you. If the kids ever stay overnight with you, you have joint physical custody. In most progressive States, a standard goal in joint physical custody is at least 25%. Your standard every other weekend and some holidays is like 15%. This means that courts and mediators are inclined to give you more than every other weekend, if you request it.

So, when you talk about full custody, it means the other parent does not see the child and can't make decisions for the child. This will only happen if you let it happen, or are a danger to the child. It is a very serious thing, and will only happen in extreme cases.

Also, if you have joint custody, do not ever fall into the trap of referring to the other parent having full custody or "primary" custody. That is not a thing. You have joint custody. Joint implies equal because that is what you are.