Understanding wal segments

Hi List;

I'm wanting to better understand wal / checkpoint segments.

I have a cluster which has checkpoint_segments set to 32 and wal_buffers set
to 24.

I see consistently 66 files in pg_xlog and I've recently implemented wal
archiving and so far there are 41 segments/files in the wal archive dir.

What's the relationship between wal_buffers and checkpoint_segments? even
though the max distance between checkpoints is 32 segments, is there
something that controls the number of files/segments in the pg_xlog dir ?

Thanks in advance

/Kevin