Magazines are written for the general public. They often have a lot of advertisements in them.
Journals, on the other hand, are targeted to students or professionals working in a particular field. The usually have very few ads in them. The articles usually include bibliographies at at the end and the author's or authors' credentials (where they went to college and where they work) are given.
Sometimes a journal is peer-reviewed which means that all of the articles have been read and approved for publication by experts in the field.
Interested in more information? See the Fake News library research guide.