Harden is the fancy industry word that means to take your HDL and using a tool like OpenLane turn it into the GDS2 files necessary for manufacture by a foundry.
I've really enjoyed the whole process, I've learned a lot. For a long time it’s been something I've wanted to do but the idea of just going at it on your own is a bit daunting. You're not really going to know what you're going to get out of it. And you're not going to know if what you've actually done is correct, so having an option to take a course with some other people has been a really great way of learning it.