The basic differences can be boiled down to types of information, cost, and a review process.
An online database will contain articles from newspapers, magazines, and journals that are not available for free elsewhere online. The library has to pay for access to the databases so that we can get this information online. In addition, the material found in a database has been through some sort of review process before it was published (in print or electronically).
On the other hand, information found on Web sites is usually free and does not necessarily go through ANY review process. Information found on Web sites can range from professional to personal and might include everything from current news to advertisements to chat rooms. That’s why it is so important to think critically about your sources and evaluate Web sites before you use them in your research.