So, we know what criteria we have for our feeds, but how will Drupal know which content meets that criteria? Let's discuss two possible methods.
A pick-me flag is a content field that's purpose is to highlight the fact that the content applies to something specific, and so is the flag for selecting it. It is represented by a Boolean field, which contains True (-1) or False (0), so that you can think of it as either on or off. It is typically represented by a checkbox.
So, for our use, we could add a field called Pets to our article content type, and check the box when creating an article if the article touches on pets, and the same with a Travel checkbox for travel content.
This makes sense, and is an easy way to determine what content to select, but there is one kink in that plan. Every time a new criterion arises, it would mean adding yet another field to the content type. Things could get messy quickly.
A pick-me flag works best for a standalone...