Periodicals are publications that are published periodically at regular intervals… hence they are called periodicals. Periodicals include popular items such as newspapers and magazines and scholarly items such as academic journals. These documents often include volume and issue numbers to help you know the sequence in which they were published. Periodicals may be published weekly, monthly, quarterly, etc.
You may be familiar with some popular types of periodicals such as newspapers and magazines, which tend to focus on current events and popular trends in society. Academic journals are periodicals that have a more scholarly focus and feature literature reviews and research studies that investigate specific trends within a particular field or discipline.
As technology continues to change so does the format in which you find many periodicals. You may still find some published in paper format but nowadays more and more are being published electronically and stored within library databases. Therefore, you must use library databases in order to access them.