What exactly Shallow content is ?

Web2.0 & short article is hit by Panda update. Google call it Shallow content

Google Panda Update 2.2

then i search about it and this i found
Just because an article is long doesn’t mean there’s more value. Just because an article is short doesn’t mean that it’s shallow. Sometimes long articles are long merely for the sake of it. Sometimes short articles are jam packed with great information and resources

any one tell me What exactly Shallow content is ?

Shallow content would be content that does not have any relevant information. Shallow content may have something to do with someone intention. Search engines do recommend that people post content that are useful and helpful to their users. If someone you're posting content for the sake of getting back-links or your primary reason for posting those kind of content is to get back-links. Those kind of content may fall in the category of shallow content because you don't focus on producing content that are quality or content that will satisfy the needs of search engine users.

"Shallow content" is essentially virtual garbage.