By default your user is not following any content unless you are mentioned, you reply to a topic or you spend 2 minutes reading it (this can be configured on your preferences).
Latest section is not intended to be used to track the topics that you care about, but to list every topic.
The same latest sections can be found in each category, listing all topics within that category.
In order to follow the content you care, you need to set categories and tags as Watching or Tracking, this will place new content from the places you care on the Unread section.
In the upcoming version of discourse, a convenient sidebar will display this content in a more accessible way: