ConstReadonlyDEFAULT: "default"Specifies that this header or footer shall appear on every page in this section which is not overridden with a specific even or first page header/footer. In a section with all three types specified, this type shall be used on all odd numbered pages (counting from the first page in the section, not the section numbering).
ReadonlyEVEN: "even"Specifies that this header or footer shall appear on all even numbered pages in this section (counting from the first page in the section, not the section numbering). The appearance of this header or footer is contingent on the setting of the evenAndOddHeaders element (§2.10.1).
ReadonlyFIRST: "first"Specifies that this header or footer shall appear on the first page in this section. The appearance of this header or footer is contingent on the setting of the titlePg element (§2.10.6).
This simple type specifies the possible types of headers and footers which may be specified for a given header or footer reference in a document. This value determines the page(s) on which the current header or footer shall be displayed.
Reference: https://c-rex.net/samples/ooxml/e1/Part4/OOXML_P4_DOCX_ST_HdrFtr_topic_ID0E2UW2.html
XSD Schema