Periodicals are a broad category of published information that comes out on a pre-determined, scheduled basis (i.e., periodically). Some periodicals come out daily (e.g., many newspapers), whereas some will only come out annually (e.g., some small scholarly journals). All information resources bring their own unique purpose, and it's important to understand how they differ from one another so that you can be a savvy and efficient researcher.
Periodicals are normally broken into three broad categories:
- General: Written by journalists for a general audience. You don't need to have specialized knowledge to be able to pick one of these up and read it. Examples of this include daily or weekly newspapers, as well as many "super market" types of magazines like Time or Scientific American. Will include ads that are of potential interest to many.
- Trade: Written by AND for professionals in a particular field. They will frequently include specialized vocabulary (i.e., jargon) relevant to that field. You will generally need to have at least a cursory knowledge of that field's background and foundation to really understand these articles. They'll also generally include ads that are targeted to this niche field. Many trade journals are published by a professional society. In music, these are frequently divided by type of instrument, such as The Double Reed (published by the International Double Reed Society for people who play oboe and bassoon) or Horn Call (published by the International Horn Society for horn players).
- Scholarly: Written by experts in a field for an expert audience. Will definitely include specialized vocabulary and require the reader to have a firm background in the field. Articles are peer-reviewed (i.e., experts read and comment on an article manuscript to determine whether it should be published). Articles generally include extensive reference lists, which help to show how this particular article relates to other specialized knowledge and how a scholarly "conversation" evolves in publications throughout time. Generally few ads are present, but if they are then they are very specific to that field.