Hi Becky,
The membership names are based on the number of posts you have made on ScubaBoard. As you make more posts to the board, your member name will change. The membership names fall in the order of Junior Member 0 - 30 posts, Member 30-100 posts and Senior Member 100+ posts. It's actually just a way to give the people who post to the board a sense of community and a feeling for who has been around a while.
I hope my explaination helps you understand the structure and purpose and I hope to see you around again. Feel free to post any questions you may have and answer any questions others post. The ScubaBoard is here so that divers can help each other whenever there is a need.
Cheers,