It's not always obvious what type of "periodical" is referenced. The list below gives some clues to recognize each type but is not meant to be definitive. Science, for instance, is a magazine, but it is definitely a top scholarly journal.

• Newspapers are the easiest since they use date, section, and column number designations. Often they are dailies as opposed to the weekly or monthly publication schedule common to magazines and journals.
• Magazines differ from journals in the level of content. Magazines include articles but are mostly current news, listings of professional meetings or programs, society business (when published by a professional society), and lots of advertisements. Almost always, each issue begins with page 1; with a weekly, this means 52 "page ones" per year, so it is important to give the issue as well as the volume number.
• Journals (sometimes called "transactions" or "proceedings") are scholarly publications for the researchers in their respective fields. Their issues are often all articles but occasionally will have editorials or short news sections. Generally each volume begins with page 1 and the pagination continues through each new issue until a new volume begins. Many citation styles ignore the "issue" of a journal and only give volume and page numbers.

Most magazines, journals, and newspapers still have a print version. Many are both print and online. Some were "born digital" and only have an online presence. It would seem to be simplest to use one citation format for all types BUT one size does not fit all. Print formats usually have volumes, issues, and pages. Online formats sometimes have volumes and even issues but often don't have pages, just links. The situation becomes more complicated when the online version may have added material that the print did not: video, color graphics, etc. Therefor, it is important to distinguish between formats so that your reader can find the reference you really cited, not a later or earlier version that has or lacks what you found important.