Could be fixed rate that expired and had to be renewed, but with a new rate.
In the US a fixed rate does not expire. At the end the loan has been repaid. I do not know of they are in the US.
How does that work? You take a loan, negotiate a rate (say 3%) upfront, and you have this rate as long as the loan is not payed?
Yes, though I’m not sure what you mean by not paid. You have monthly payments for the loan.