This period of time is sometimes referred to as a database's coverage . Be aware of when each database's coverage starts. You may need to consult print resources to locate your materials. However, you need to know how frequently each database is updated. Be aware that most databases have some lag time, i.e. it takes some time for very recent materials to be included in the database.
Most databases are indexes .
It does not give you the text of books. They don't give you the articles. Search engines provide links to web pages. They don't provide the pages. Some databases provide data or the full text of articles.