You should consult the help center.
There are three types of content on
your Wall, and you can control who can
see them by following the instructions
Posts your friends leave. Posts, comments, and other things your
friends leave on your Wall are
controlled by a group of settings in
the "Sharing on Facebook" section on
the Privacy Settings page. To
adjust these settings individually,
follow the "Customize settings" link
and scroll down to the "Things others
Posts you create. Status updates, photos, links and other things you
post are controlled by the "Posts by
Me" setting in the "Sharing on
Facebook" section on the Privacy
Settings page. Follow the
"Customize settings" link to adjust
this setting individually. Keep in
mind the "Posts by Me" setting is a
just default for things you post. You
always have the option to adjust the
privacy for individual posts before
you share them by clicking the lock
icon directly from the Publisher.
Recent Activity. These stories are determined by the privacy setting of
the content itself. For example, if
someone would already be permitted to
see a particular photo and comments,
then they would also be able to see
the Recent Activity story about you
making a comment on the photo. While
you cannot completely turn off recent
activity stories, you can remove a
particular story by clicking the
"Remove" button that appears to the
right of the story after you move your
mouse over it.
[Source - Who can see my Wall? ]
In simpler terms your wall can only be seen by you and whatever friends you allow to see your wall.
Your news feed is what everyone allows you (based on your settings in their privacy page) to see.