To have complete access to the eNotes site, you must purchase a membership to the site. This membership allows you to obtain full access to any of the pages on the site and pose as many questions to the editors on eNotes regarding any supported area (literature, math, science, history, etc). Without the purchase of a membership, the site limits a visitor's ability to traverse the site free of charge. Also, as a member, the questions you poses are considered to be of the highest priority and are asked by eNotes to be answered first.
While this may seem questionable to you, I assure you that there are MANY qualified editors on the site who devote much of their time to helping both students and teachers with the material they are looking for. The information that you are provided with, as a member, is immeasurable. You are provided (for example in literature) complete pages regarding characters, summaries, themes, history, introductions, and critical analysis on the text in question. Basically, you are getting access to complete study guides. As you can see, eNotes can be your one-stop "shop" for many different things.
I hope that this answers your question completely.