How to list articles by an author in a views? In Drupal 7, I have defined a node type 'article' which has an 'author' field (The author is not a user, but just a 3rd party contributor). Now I want to list articles by the each author in a view. How can I do that?

I know that it can be done somehow using contextual filters but got quite perplexed so  appreciate your help.
In your case, i would create a Vocabulary "authors" and add them with a Auto Tag Widget to the Content Type. And add the Authors as a Taxonomy Tag. There are much more Handly then Text Fields.
Then you can easily Create a View with the author Tag. And much more, you can also add more fields to the Taxonomy such as author Picture and Author Description.