Open Gym format?

Hey Guys, I am starting boxing on Monday and I emailed the dudes to find out a bit about the club. Basically its open every night for 3 hours and they said it is an "open gym" format where you rock up and train.

You can have 1-2-1 sessions for $20 an hour but what I don't understand is what is an open gym?

Do I just get left on my own to punch bags and skip or do I actually have someone showing me technique and some sparring?

Just access to the bags and other equipment, no instruction or schedule.