Hi Lisa, welcome to Rescreatu! We're super happy to have you. :)
Your username is simply the name you use to log into the game. It displays all over the site (including this forum, your profile, the Shoutbox, etc.), and other users can use this name to find you and your profile or send you things such as ResPal requests (friend requests), Rmail (private message), and even items. I hope this was helpful! Please don't hesitate to ask if you need any more help or have any specific questions.
A great way to get started here is to explore the forums. The Introductions forum is particularly great since we've got several new users guides here. And, if you're old enough, the Shoutbox has many helpful users as well! For now, I recommend reading over our rules if you haven't already. They can be found here: http://www.rescreatu.com/rules.php
I hope you're enjoying yourself so far, and I'll see you around!
Normal User
