Anyone can create an account, but you can do most things as an unregistered contributors, or IPs.
Disadvantages to being an IP
The biggest of all is that your Internet Protocol address, or IP, shows. This can help find the IP's location! (It's also how unregistered contributors get the nickname "IP.") Another disadvantage is that there are certain functions that they can't do, and there's no way that they can become admins. It's impossible to give an IP any user rights.
What IPs can do
IPs can edit unprotected pages, create pages, and other basic functions for editing. They can also comment on blogs. Some edit functions, however, are for registered contributors only.
What IPs can't do
IPs can't add pictures or videos to pages, or upload pictures. They can't create blog posts. That's why you should create an account. You must be 13 or older to register, though