Everfree Empire is the "normal" roleplay section. You don't need approval of any sort to post or add characters. This section also encompasses the Advanced Roleplays area. Advanced roleplays require each post to be a minimum of 800 characters. The rest of the Everfree Empire roleplays require 200. As soon as you hit "Muffin" rank (5 posts), you will be able to participate here.
Equestrian Empire has stricter requirements, as it is the "canon" roleplay section. It follows all of the Everfree Empire rules, as well as having its own code of additional rules. It allows members to pick up cast characters as their own character, as well as OCs that can interact with the cast of MLP:FIM. This section also has a smaller population of users, allowing the users in that section to become quite close. Equestrian Empire has a character minimum of 300.