what is “tag”?

some definitions of ‘tag’

tag (noun): A string (text) that is associated with something else (eg a book, web page, even another ‘tags’). The specifics depend on the implemenation, but a ‘tag’ usually may not contain spaces, and often may only contain [A-za-z] or even [a-z], but sometimes it can contain anything, such as quotation marks or non-ASCII unicode characters. When referring to a ‘tag,’ one is usually referring to a specific string, but sometimes one is actually referring to a set of normalized ‘tags’; i.e. with plural words stemmed.; An XML or HTML ‘tag’… these are the basic building blocks of XML
tag (verb): To apply a ‘tags’ (see first noun definition) or multiple tags to something; To apply any type of metadata (such as ‘tags’ see first noun defintion) to something… this may or may not be done using ‘tags’ in the XML sense.

does this clarify the situation? gotta love the last defition