The MDB file format is a proprietary file format used by Microsoft Access, a database management system (DBMS) from Microsoft. It stores the entire database structure, including tables, queries, forms, reports, macros, and modules (VBA code). MDB files are used to store and manage data in a relational database model. They support various data types, including text, numbers, dates, and binary data. The format has evolved over different versions of Microsoft Access, with newer versions using a different internal structure than older versions. While MDB was the primary format for Access databases for many years, Microsoft has since introduced the ACCDB format, which offers improved features and performance. However, MDB files are still widely used, especially in older applications and systems. Opening and manipulating MDB files often requires Microsoft Access or compatible database software.