What would a line of credit actually do?

I’m in my last year of studying. For the first time ever, OSAP did not pay my full tuition. I found out they “don’t pay the full thing”. This is new to me.

I do not have any money. Like none. My parents don’t help me. OSAP gave me $400 in grants and I haven’t spent it yet and it’s probably gonna go to my outstanding balance of tuition, but if I do that, then I would be starving and stuck in the house with no bus fare.

The school told me to get a job or get a line of credit. I do not want to work while I’m in full time studies, so line of credit it is….?

BUT! I don’t understand it fully. They give me $20,000 (for example) and then what?? I just have it there? In my bank account? Do I have to repay what I borrow, or everything? Do I pay interest on what I take or does the whole thing have interest? Do I ask for the amount I want and they give it? Do I have to pay it monthly like a credit card? (Idk about credit cards, I don’t have one)

Can you explain like I’m a tiny kid so I understand…