As ALA defines it, information literacy is a set of abilities requiring individuals to “recognize when information is needed and have the ability to locate, evaluate, and use effectively the needed information.” To be information literate, then, one needs skills not only in research but in critical thinking.
Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work. It functions as a form of self-regulation by qualified members of a profession within the relevant field.
In order to qualify as an academic or scholarly source, an article must go through the peer review process.
Credible sources are written by authors respected in their fields of study. Responsible, credible authors will cite their sources so that you can check the accuracy of and support for what they've written.