Voluntary.
In the context of psychiatric hospitalizations, the term voluntary, or voluntary admission, or conditional voluntary, doesn't actually mean that your time in that facility will be voluntary, because you can't just leave whenever you want to. The specifics of this can change significantly from state to state, but generally speaking, when someone signs a voluntary admission to a psychiatric facility, they can't just leave. They will have to ask for permission to leave. And once that request for discharge is submitted, then it essentially starts a clock, a specific window of time during which that facility has to decide whether or not they are going to allow you to leave. That window of time is determined by state law. So it could be 24 hours, or 48 hours, or 72 hours, and it may or may not include weekends and holidays.
And so, what happens if you are in a psych facility as a voluntary admission, you request discharge, and the facility decides not to let you go? Typically, when that happens, the facility converts your voluntary status to an involuntary status, which means that the facility has chosen to begin a process that will allow them to keep you detained inpatient until such a time where either they decide to let you go, or you get to appear before a judge at a commitment hearing. So, signing a voluntary does not mean that you can leave whenever you want to, you have to formally request discharge, and once you do that the facility has an opportunity to convert your voluntary to an involuntary.
I want to be clear though, this decision of whether to sign a voluntary or risk being detained involuntarily, that is an incredibly personal decision. There is no one right answer to this. But whatever decision is right for you read everything before you sign it, and if you need accommodations to do that, ask for them. And if possible, keep all of the paperwork that you are given and take note of what you are told about this process because all of that might become useful if you reach the point of a commitment hearing.