What causes the value of "reader.NodeType" to have 1 of the following 3 values when reading a record an XML file: EndElement, Whitespace, Text?

I am writing my first C# Console application and I'm trying to understand what causes the value of  "reader.NodeType" to have 1 of the following 3 values when reading a record from the following XML file:
1) EndElement
2) Whitespace
3) Text

Snippet of code
------------------
XmlTextReader reader = new XmlTextReader("C:\\rbc.xml");      
            StreamWriter sw = new StreamWriter("C:\\output.txt");
            while (reader.Read())            
            {
                if (reader.NodeType == XmlNodeType.Element)
                {
                    if (reader.Name == "csc:check_number")

Sample XML file:
--------------------------
<?xml version="1.0"?>
<csc:Cion_Index_File
    xmlns:csc="http://rt.csc.com/xml/Cion_Index_File">
<csc:header>
    <csc:version>1.0</csc:version>
    <csc:customer_name>              </csc:customer_name>
    <csc:request_id>DD </csc:request_id>
    <csc:creation_date>20100909</csc:creation_date>
    <csc:creation_time>082723</csc:creation_time>
    <csc:creation_host>bbd-ce</csc:creation_host>
    <csc:content_type>CHECK</csc:content_type>
    <csc:item_count>602</csc:item_count>
    <csc:image_file_name>0.img</csc:image_file_name>
    <csc:input_request_file></csc:input_request_file>
</csc:header>
<csc:item>
    <csc:processing_date>20100907</csc:processing_date>
    <csc:item_sequence_number>000002500480784</csc:item_sequence_number>
    <csc:account_number>00000000000004444444</csc:account_number>
    <csc:check_number>000000903485725</csc:check_number>
    <csc:amount>0000305200</csc:amount>
    <csc:routing_transit>896888848</csc:routing_transit>
    <csc:bank_number>7777</csc:bank_number>
    <csc:transaction_code></csc:transaction_code>
    <csc:data1></csc:data1>
    <csc:data2></csc:data2>
    <csc:data3></csc:data3>
    <csc:userField></csc:userField>
    <csc:image_offset>17737464</csc:image_offset>
    <csc:image_length>019792</csc:image_length>
    <csc:image_side>A</csc:image_side>
</csc:item>
</csc:Cion_Index_File>