title: Mongo finders and criteria
body: <p>I use MongoDB in my rails application with Mongoid mapper. But I don't understand <code>finders</code> and <code>criteria</code> of querying. For example in mongoid documentaion in section <code>Finders</code> is query <code>Model.all</code>, but if I use that(for example <code>User.all</code>), console return criteria and not the result:</p>
  
  <pre><code> =&gt; #&lt;Mongoid::Criteria
    selector: {},
    options:  {},
    class:    User,
    embedded: false&gt;
  </code></pre>
  
  <p>But if I use finder <code>Model.first</code> or <code>Model.last</code>, console return specific result. (<code>User.first</code> return specific user, with its fields, as <code>:email</code>, <code>:username</code> and other). Why <code>Model.all</code> wrote in documentation as <code>finders</code>? And what I need doing if I need get all <code>Users</code> or for example <code>Posts</code>?</p>