Footnotes appear the bottom of a page whereas endnotes will appear at the end of the article, chapter, or back of the book. Footnotes are more common in scholarly works due to their ease of access for quick reference. The limiting factor for footnotes is the amount of physical space they occupy on each page (additionally footnotes must be located on the same page as their reference point).
Endnotes avoid the shortcoming of footnotes but are not as quickly accessible. In texts with large numbers of citations, finding a particular note can be burdensome for some. Hyperlinking of note numbers in electronic resources has helped to alleviate this issue.
There is no right or wrong answer in choosing your note-style. For most writers it comes down to personal preference and knowing how much material will be cited.