Is wiki the same as Wikipedia?
Although sometimes these terms mean the same thing, quite often wiki refers to the type of software that allows users to edit content, while Wikipedia is an online encyclopedia that uses this type of software. Therefore, you can use wiki software to create any kind of website not just encyclopedias.
Is OneNote a Wiki?
If you grant other users access to your document, OneNote can be considered a Wiki, the same way Google Docs can. The main factor to decide if software is a wiki or not is if it allows user collaboration.