A magazine is a publication issued periodically that has scientific and technical articles that are translated into a language suitable for a more general audience. Magazine articles are usually written by a journalist rather than the engineer/scientist who has done the research. Some magazines are aimed at the lay public while others are suitable for technically trained people.
A journal is a publication issued periodically that reports original research. Manuscripts submitted by researchers are scrutinized by an editor and a referee before they are accepted for publication. This is known as the peer review process. The articles are very detailed and include detailed experimental procedures. It is aimed at a very specialized audience of researchers in the field.