what do vertical lines refer to in database diagram view
The answer for to your question is further down in the article:


  Endpoints The endpoints of the line indicate whether the relationship is one-to-one or one-to-many. If a relationship has a key at one endpoint and a figure-eight at the other, it is a one-to-many relationship. If a relationship has a key at each endpoint, it is a one-to-one relationship.


The key represents the "one" and the figure-eight (or infinity symbol, I presume) represents the "many".

The relationships aren't tied to the visually closest column name in the diagram, but to the column with the same name in each table. For instance, the one-to-many relationship between publishers and titles is tied to the pub_id column.