Makes you an informed researcher/applicant
Provides perspective by situating your work within the knowledge base (theory & practice) of your field
Supports your research idea/proposal or identifies a gap needing further research
Provides ideas for research design; for example, quantitative or qualitative approaches or instruments to use
Provides credibility to grant proposals
Scholarly (aka academic) articles are written by and for academics, researchers, and experts in the specific topic or broader subject area of the article.
Peer reviewed (aka refereed) articles are those which have been reviewed prior to publication by other experts in the topic of the article. Often reviewers are external (not members of the journal's editorial staff or board).
Note: Not everything in a journal is peer reviewed; letters to the editor, book reviews, news items, and other short works without listed references are typically not peer reviewed the way more substantive articles are.