Databases (or article indexes) are online tools to help you find journal articles (along with conference papers and other sources) on a given topic. We have many databases and some index millions of articles, conference papers, patents, media, etc.
Start with UC Library Search?
If you are looking for a few articles, try UC Library Search first, since it indexes articles as well as books. Leave it on the "Articles, Books and More" option rather than changing to "Library Catalog."
Simple 1-2 keyword searches will bring back thousands of results, so you can use the Advanced Search to add more keywords for a more targeted, relevant set of results. You can also use the facets to the left of the results if you want to limit to peer-reviewed articles, or articles that you'll be able to get online. Here's an example.
Try the Article Databases?
While the UC Library Search is good if you need a few articles, they don't include everything journal and article that you may need for research. The article indexes are better for deeper and more comprehensive searching, and in some cases offer more options to refine and limit searches. A data may cover all disciplines or only cover a subset of disciplines, like Ei Village for engineering, PubMed for biomedical sciences, or SciFinder for chemistry. More databases are listed on the various subject guides.