Filters to automatically display only certain filetypes

How can I arrange it so whenever I open a list of files, only certain files are displayed. For example, only JPEG images.
Do I use a Lister or a Style? And then how do I implement that?

Secondary question: I am confused as to the difference in features/edits between Folders, Listers, and Styles. When do I use each of these 3

As to the first question, this thread might be of interest:

Please ask separate questions, so it´s easier to keep track of certain topics.