A database is a collection of information, organized and limited in some way, which is usually both keyword searchable, and navigable by metadata (descriptive information). Scholarly research databases are designed for and by scholars in a specific discipline. They level up your research by providing specialised tools, curated collections, and useful descriptive information that you can use to find articles on a topic.
It will contain the literature of a discipline, organised and described in a way that's appropriate to that discipline, with tools useful to it. These vary greatly in size and scope, and provide tools that serve the disciplinarch scholars they support. (Psychinfo has limits for 'population group', and history has limits for 'era', for example.)
Many database can be searched together if they are from the same publisher (Ebsco, Proquest etc), but in doing so, you lose access to the discipline specific tools that make these databases so useful.
UVic Libraries subscribes to these, and often, their contents, so that you can find articles and other sources quickly and efficiently. The key databases in a discipline also link to full text articles from other databases, publisher website, digital archives and library collections, so that you can spend less time looking for articles, and more time reading.