SQL Server Native Client ODBC Data Sources
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
A SQL Server data source name (DSN) identifies an ODBC data source containing all of the information that an ODBC application needs to connect to a SQL Server database on a specific server. There are two ways you can define an ODBC data source name:
On a client computer, open Administrative Tools in Control Panel, and double-click Data Sources (ODBC). This will open the ODBC Data Source Administrator, which you can use to create a DSN.
In an ODBC application, call SQLConfigDataSource.
A SQL Server data source contains:
The name of the data source.
Any information needed to connect to a specific instance of SQL Server.
The default database to use on a specific instance of SQL Server (optional).
Settings such as which ANSI options to use, whether to log performance statistics, and so on (optional).
An ODBC application is not required to connect through a data source. However, the application must provide the same connectivity information to an ODBC connect function that the driver would otherwise find in a DSN.