So, what is "peer review"? 

When an author submits a manuscript to a journal for possible publication, the journal editor forwards the paper to peer subject scholars for review. They give their opinion on if it should be published or not based on the paper's quality, validity, its contribution to the field, etc.

Many databases allow you to filter your results to "peer-reviewed" only. (The Ulrich's Serials Directory database also tells you if a journal title is a peer-reviewed jounal.)

So, what is an "empirical" article? 

Empirical research is when a researcher personally conducts a study and reports on the findings of the experience as opposed to reporting on the the work of others.

Some databases allow you to filter your results to "Empirical Study" under the "Methodology" filter, for example.