Schema of a XML file

I have an issue understanding the way my output of the query I am running :

SELECT [Customer].custid AS [custid],
[Customer].companyname AS [companyname],
[Order].orderid AS [orderid],
[Order].orderdate AS [orderdate]
FROM Sales.Customers AS [Customer]
INNER JOIN Sales.Orders AS [Order]
ON [Customer].custid = [Order].custid
WHERE 1 = 2
FOR XML AUTO, ELEMENTS,
XMLSCHEMA('TK461-CustomersOrders');

This is the output :

<xsd:schema targetNamespace="TK461-CustomersOrders" xmlns:schema="TK461-CustomersOrders" xmlns:xsd="http://ift.tt/tphNwY" xmlns:sqltypes="http://ift.tt/1o3ANS9" elementFormDefault="qualified">
  <xsd:import namespace="http://ift.tt/1o3ANS9" schemaLocation="http://ift.tt/1o3ANSc" />
  <xsd:element name="Customer">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:element name="custid" type="sqltypes:int" />
        <xsd:element name="companyname">
          <xsd:simpleType>
            <xsd:restriction base="sqltypes:nvarchar" sqltypes:localeId="1033" sqltypes:sqlCompareOptions="IgnoreCase IgnoreKanaType IgnoreWidth" sqltypes:sqlSortId="52">
              <xsd:maxLength value="40" />
            </xsd:restriction>
          </xsd:simpleType>
        </xsd:element>
        <xsd:element ref="schema:Order" minOccurs="0" maxOccurs="unbounded" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>
  <xsd:element name="Order">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:element name="orderid" type="sqltypes:int" />
        <xsd:element name="orderdate" type="sqltypes:datetime" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>
</xsd:schema>

I've spent more than 4 hours searching about these without any result.

I am not able to understand the functionality behind :

targetNamespace - why do I need it if I am using xmlns and I am using prefixes to all my other elements

xmlns:schema - Why do I need a schema for the namespace ? I am already defining one for the XSD, which I use as a prefix to my elements already

importing the namespaces : why do I need that if I am already defining the namespaces previously ?

There is no place where I can find some details about these so I can understand them, there's only explanation for simple prefixing and namespacing a prefix, but I've yet to find an explanation for an XSD such as this.

I've worked very little with XSD-s and I cannot understand how these things work together Sorry for bad question, but I've wasted more than 4 hours trying to understand something easy, can't help myself with this one.