what do these tags do <%- xxxxxx -%>

Hi,

I see some code from some open source project.

in many of the view files(.erb) , I see the following statements.

Idont understand how they are interpreted..
are they comments, or shown on UI, or just executed?
[code]
<%- column_div :type => :primary do -%>

  <h2>People Admin</h2>

  <%= will_paginate %>

  <ul class="list people admin">
    <%= render :partial => @people %>
  </ul>

  <%= will_paginate %>
<%- end -%>

<%- column_div :type => :secondary do -%>
  <%= render :partial => 'searches/box' %>
<%- end -%>

[/code]

IN another file, they used these tags <%= xxxxxx -%>

[code]
<li class="vcard person">
  <%= person_link_with_image person, :class => "url fn" %> &mdash;
  <%- activity = activated_status(person) -%>
  <%= link_to activity,
              admin_person_path(person, :task => "deactivated"),
              :method => :put %>
  >
  <%- activity = person.admin? ? "unadmin" : "make admin" -%>
  <%= link_to activity,
              admin_person_path(person, :task => "admin"),
              :method => :put %>
  <p class="person_meta">
    <strong>Forum Posts:</strong>
    <%= person.forum_posts_count -%> |
    <strong>Blog Posts:</strong>
    <%= link_to person.blog.posts.count.to_s, blog_path(person) -%> |
    <strong>Connections:</strong>
      <%= link_to person.connections.count,
                  person_connections_path(person) -%>
  </p>
</li>
[/code]

Look at the rendered source to see the difference immediately.

<%- strips whitespace in front of the tag.

-%> strips trailing whitespace, including the newline.

This is useful for rendering plain-text emails without a bunch of
gibberish whitespace.

Best,
jeremy