To connect an Access database (.accdb file) from a C# application, you need to download and install the 2007 Office System Driver from Microsoft. This will allow you to connect to and query the Access database. A database stores data in an organized format using tables. Tables contain rows and columns to hold related data. The SQL language is used to query and manage data in databases. Common SQL commands include SELECT to retrieve data, INSERT to add new data, UPDATE to modify existing data, and DELETE to remove data.