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.
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.
For some research projects you may be required to use primary sources. How can you identify these?
A primary source provides direct or firsthand evidence about an event, object, person, or work of art. Primary sources include historical and legal documents, eyewitness accounts, results of experiments, statistical data, pieces of creative writing, audio and video recordings, speeches, and art objects. Interviews, surveys, fieldwork, and Internet communications via email, blogs, listservs, and newsgroups are also primary sources. In the natural and social sciences, primary sources are often empirical studies—research where an experiment was performed or a direct observation was made. The results of empirical studies are typically found in scholarly articles or papers delivered at conferences.
Secondary sources describe, discuss, interpret, comment upon, analyze, evaluate, summarize, and process primary sources. Secondary source materials can be articles in newspapers or popular magazines, book or movie reviews, or articles found in scholarly journals that discuss or evaluate someone else's original research.
(source: Ithaca College Library https://library.ithaca.edu/sp/subjects/primary)
For a list of more examples, see Loyola Marymount University in Los Angeles Libraries' Libguide
Technical reports describe the process, progress, or results of technical or scientific research. Include in-depth experimental details, data, and results.
Technical reports are usually produced to report on a specific research need. They can serve as a report of accountability to the organization funding the research. They provides access to the information before it is published elsewhere.
Technical Reports are usually not peer-reviewed. They need to be evaluated on how the problem, research method, and results are described.
Taken from Penn State University Libraries Engineering and Information Science and Technology Libguide http://guides.libraries.psu.edu/techreports