What custodial means
Custodial parent traditionally means the parent a child lives with most of the time; noncustodial means the other parent. The labels are older shorthand, and many states have moved away from them toward language like primary residence, parenting time, or time-sharing, which describe the schedule without implying one parent won and the other lost.
The terms still show up in older orders, in tax and benefits rules, and in everyday conversation, so it helps to know them even where courts no longer use them. What actually governs your situation is the schedule and decision-making in your order, not the label attached to it.
Example: a parent called noncustodial in a decade-old order may still have substantial, regular parenting time; the word describes primary residence, not the amount of involvement. Documenting your actual time with the child matters more than the term on the page.
Because usage varies so much by jurisdiction, check what your own state and order actually say rather than assuming the labels carry the same meaning everywhere.