I went to an online high school called Insight School of Washington which is run by k12 (they bought it in my sophomore year and we ended up switching systems, which was a big pain, but that's another story
).
The course curriculum usually included free e-books. Some courses did actually get me free physical books that I'd send back at the end of the semester. My physics class used an online book, my history courses usually involved giant physical textbooks, and my English classes used a mixture of both online and physical books. All of which were free
Speaking of free, they also sent me a computer to use and a printer. Both were expected to be given back when I graduated and they provided shipping labels. I think as the years went on they started asking who actually needed a laptop to use, but when I first started they just sent them out to everyone.
If you've heard of Blackboard/Elluminate, that's what they used for classes. Each teacher would hold a 'class' once a week. Most teachers didn't use video, but talked and used a PowerPoint presentation. In Washington they recently made it required that students go to at least one hour of 'class' a week. For people who couldn't make it to any of their schedules classes, there were labs that ran basically all day for math and English that counted for that credit.
There were discussion boards. Each unit had a 'raise your hand' section for questions related to the course work. Every now and again there would be a separate forum for students to answer a question posed by the teacher or to talk about what they thought of a book. Not sure if that gives a good enough image of it, but basically, yes, there are discussion boards/forums. Although there wasn't a forum for the whole school, just for each class. They did have a Facebook page for students to connect on, though.
And you didn't ask, but I think it's sort of relevant so I'll just say it. There were some in person events. It's a state wide school, so often they weren't in my area, but they existed. Those events include graduation and prom (all grades could go to prom, too). Graduation was held at a community college gym and prom was in another building at the same college. They also did things like discounts for game tickets and trips to the aquarium, that sort of thing. So kind of like field trips.
Anyway, that's what it was like at my school, at least. I just graduated in June, so pretty recently. Hopefully that answers your questions thoroughly enough and makes sense, but if there's anything else you want to know, I'm happy to answer!