At this point in time, you will see more functionality on the app than you will on the web version. They plan to release a full web version in the Fall of 2014- at this point it is in beta format.
As you can see in the screenshot below, it has a very simple menu interface.
You can find content or, load a "save to subtext" browser clipper to add content from the web. This is a very cool feature- you are not limited to curated content from Subtext.... any digital content you find on the web can be used within Subtext.
To create a class, you simply look for the groups block and click on "create group". It will generate a code which your students can use to sign up for your class. When students join, they will see what content you have shared with them to read.
When you click on the book or article that has been added to your library, you can then open it up and look for the discuss bubble. (This is a free feature)
After clicking the discuss icon, this is a sample view of what you will see. (This particular example shows another Subtext reader who has posted some comments) If I choose, I can simply reply and add to the conversation. (I blacked out this user to protect privacy).
When you find an article, it is very easy to share with your groups.
Once you have chosen a text and shared it with your group, you as the teacher can start by adding some discussions. Check out the types of interactions you can add- comments, questions, polls & quizzes.
To get the most functionality- data tracking and assignment features you have to buy licenses. However, even the basic free functions are impressive.
One more thing- you can use Subtext within Edmodo! I haven't tried this out yet, but I can imagine it is a very slick way to use it!!