'Members map' options and 'Start a swap' page

Hi all,

Can anyone explain me that ?

1. What is the difference between the options "Show all members" and "Show only swap partners" in the members map.

2. Why "Start a swap" page apparently shows only the ones which are "swap partners" ?

3. The same as above when I choose " Show only members about who I wrote a comment".

Thanks in advance,

Marcelo