What exactly are footnotes and just how to arrange them in the text of report or abstract?

What exactly are footnotes and just how to arrange them in the text of report or abstract?
What exactly are footnotes and just how to arrange them in the text of report or abstract? A footnote is definitely an additional bit of text, the information of which specifies the web link. Footnotes are printed in various locations: within the text, in the bottom for the web page, in the end associated with the paper. Huge difference in design and location of footnotes ...