Journal articles are usually comprised of original research that is focused on a very narrow aspect of a topic. These articles are written by scholars in a given field and are very authoritative and reliable. Journal articles are published more quickly than books, offering more current information.
Magazine and newspaper articles are written by staff and freelance writers who are not experts in the subject matter they are writing about. They are less authoritative and not considered scholarly sources. However, you can find very current information in these sources because they are published frequently (especially newspapers) and do not go through a lengthy review and publishing process. These sources will be particularly helpful when you are researching current events and general interest topics that may not be covered in more scholarly publications.