Can you please give me the definitions of

Not necessarily, no. EzineArticles, Hubpages, Squidoo, InfoBarrel, BBC News, New York Times, etc, are all (probably) considered "authority sites" from the perspective of the search engines. The latter two also from a human perspective (though how much a person trusts/respects a particular news site is obviously dependent on that individual's taste and political bias/persuasion). None of the aforementioned are really "niche-focused"; they have articles covering all manner of topics.

When people talk of "authority sites", though, they're normally referring, I think, to sites that fall into the first category.

And again: not necessarily. Crappy "XFactor" sites", filled with nonsense content and/or where the webmaster has failed to comply with the AdSense policies usually will be "slapped" at some point (and by that I mean have their rankings "penalised" in or de-indexed from Google and/or other search engines, or - arguably worse - will result in you having your AdSense account terminated). But I find it hard to believe that Google will slap even the smallest sites if the content is "passable" and those in charge of them aren't engaging in on-site b1ackhat SEO techniques, or anything else which is very clearly a violation of Google's various service policies.

People seem to think XFactor (John) was advocating the building of sites which are kept intentionally small and information-thin, though - and that's a gross misconception on their part, I think. The idea is to build each site on a different, tightly-focused niche topic. Hence the term "micro niche sites" - not "micro sites". This isn't a practise used exclusively for those monetising with AdSense, though. It's often done for SEO benefits, for the purpose of diversification of one's portfolio, and also because each site becomes an asset in and of itself - enabling them to be sold off individually at a later date, if one so wishes.

Good point, but I think terms "the XFactor method" or "XFactor sites" are more commonly used these days (at least on this forum) in reference to the method/outline written about and discussed in John Robinson's (XFactor) micro-niche AdSense thread and ebook.

At least, this is what I figured the OP was referring to. :confused:

(Pity there isn't a "duplicate content penalty" for those who choose non-unique names for their various techniques and courses, eh, Alexa? *nudges* )