Books etc that people no longer need for first years?

I’ve seen this a few times and people on my course have mentioned it too. I wonder if people leaving uni, want to sell their books on? Just the same as I want to get rid of some of mine from my course. I’m starting biology this year and thought It could be a good way for people to gain books and those who don’t want them anymore .

Not sure where to post this but any ideas. Thanks