Each club has hundreds or thousands of members...but with each member...there are a few other member with which they regularly keep up with our associate with. Maybe play golf or tennis together...or their kids are friends.
So...on Clubster, each member can invite other members to be "Friends'. If they "accept" and become a friend...every time you post a comment or photo on Clubster or they post a comment or photo...you each will see those posts on your Home Page in your News Feed.
So...you should invite any members you wish to regularly keep in touch with...as Friends on Clubster