I am a new officer. What do the icons mean on officer club list?

As an officer (shield next to your name), you can promote members to officers (green button) or expel them from the club (red button). If you promote a member to officer you cannot demote them, only the president can do that. Below the list are icons to invite people from your boat list (person icon with "+" sign) and if the club is "application" club you can look and accept applicants (box icon).