<Query>
  <Where>
   <Eq>
    <FieldRef Name="ContentType"/>
    <Value Type="Text">Item</Value>
   </Eq>
  </Where>
</Query>

<Query>
  <Where>
   <And>
    <Eq>
     <FieldRef Name="ContentType"/>
     <Value Type="Text">Item</Value>
    </Eq>
    <Eq>
     <FieldRef Name="name of some column"/>
     <Value Type="Text">One of its values</Value>
    </Eq>
   </And>
  </Where>
</Query>