Refereed journals (also called peer-reviewed) are scholarly journals that only publish articles that have been evaluated by a group of experts in the field. These experts must approve an article before it is allowed to be published. These publications have a much higher level of scholarship and are far more trustworthy than non-refereed journals or magazines.
To help you make sure your articles are from refereed journals AS you're searching for them, many databases have limit options. For example:
To confirm that your journal article is from a refereed publication after you already have it, check Ulrich's for this symbol (a referee's jersey) next to the journal title: