Once researchers complete a project, they will usually (try to) publish their findings in a peer-reviewed journal. These are often called PRIMARY or ORIGINAL research articles because they are the first-publication of new research findings and are written by the researchers themselves. They may also be called EMPIRICAL articles.
Secondary sources of information describe, explain, interpret or summarize primary sources. These include encyclopedias, book reviews, commentaries, literature reviews, and any books or journal articles that simply discuss the original (previously-published) work of others. Although these can be very helpful sources for identifying primary research articles, they are not primary studies themselves.
A primary (original) research article will usually be divided into several labeled sections. The screenshot above is from the video "What is Original (Primary) Research in Criminology?". You can jump to the 3:10 timestamp to watch the "Sections of an original research article" segment of the video.
The names of the parts may vary, but a primary research article will always include a methodology section explaining how the research was conducted (i.e. what type of empirical method was used). Most secondary journal articles do not include a methods section.