PRN job?

No, it just means that you work when you are able. It also means that whenever they have a sick call or need vacation coverage you'll get called to see if you can work extra.

You'll want to clarify with them, but usually in prn jobs you tell them when you're available. They may call at other times but you aren't obligated to help out.

Some places do have certain requirements for prn; you have to work so many hours in a certain period of time, so many weekends or holidays, whatever. Of course if your regular job is, say, every weekend, you can't be expected to work your prn job then.

I'd make sure I asked during the interview exactly what they expect.

I have never heard of on-call for PRN. I work per diem-probably the same thing. I sign up for the days and hours of work I want. The unit can call me at home and ask me if I want to work, just like they call all the full-time staff. I am not obligated to come in.

Are you thinking of the On-call like some nursing departments use where you are obligated to come in if needed. Our dialysis and radiology nurses do take call where they need to be easily contacted and get paid a small wage for their time on call.