Each library database is designed for a specific purpose, and they each express that in different ways, including:
Content coverage: Some databases are general or cover multiple disciplines, while others are narrowly focused on one subject.
Publications included: Databases might include books, eBooks, dissertations, reviews, primary sources, and more. Some databases only include articles from scholarly journals, while others might include newspaper and magazine articles.
Article content: Some databases include the full text of every article provided, some include full text for some articles but not others, and some only include information about the articles (called indexes).
Search features: Different databases will provide different filters to refine search results based on the best ways to differentiate content in the database.
Ask a librarian if you need help deciding what database to use.