Footnotes are added to provide detailed comments and Endnotes for citation of sources. Check this link for more information on these two feature. In Word 2013 and Word 2010 one case insert Footnote or Endnote using the References menu and also by Keyboard shortcuts.
To insert a footnote or endnote, Click References menu and then navigate to Footnotes section. To insert a footnote, click the menu option with text as AB1 Insert Footnote.
Similarly to insert a endnote, click the Insert Endnote menu option.
The keyboard shortcuts for inserting a Footnote is Alt + Ctrl + F for inserting a Endnote is Alt + Ctrl + D.