What is a pattern portfolio?

It is more than a style sheet. My boss sent out a link to this today which includes a link to this suggesting that a pattern portfolio should have:

1. a component library
2. page examples

 
 

The first link also suggests that a pattern portfolio should be fairly baked-out in terms of deliverables too and not skimpy. Examples of it done right seem to be:

1. Bootstrap
2. Mailchimp's pattern library