An embedded database is a database technology in which database management solutions are built into an application rather than provided as standalone tools. In many cases, this effectively "hides" the database management tools from the end user.
Techopedia explains Embedded Database
An embedded database system can be set up in many ways. It can include traditional relational database designs or other kinds of storage formats. It can utilize different solutions as well; for example, a popular type of embedded architecture uses MS Access for storage and relies on VBA forms to handle data requests. Many of these systems also use various APIs and SQL tools to perform data-related tasks.
Embedded database designs are used for various purposes. Embedded database tools, for example, can be used for email archive searches, for presentation of gaming statistics or other stored game data, and for industry-specific tools like tax-preparation software packages.
IT professionals also sometimes use the term embedded database to refer to database solutions that run on mobile devices.