In Microsoft SQL Server, the user account that created the database and is responsible for managing administrative tasks related to a SQL Server database.
Each SQL Server database is considered a self-contained administrative domain and is assigned a database owner (DBO) who is responsible for managing the permissions for the database and performing tasks such as backing up and restoring the database's information.
Essentially, the DBO can do anything within the database. By default, the SA (system administrator) account is also a DBO account for any database on a computer running SQL Server. The database owner has full permissions inside a database that it owns.
To avoid the complexity of managing separate DBO accounts for each SQL Server database, you might want to perform all administration tasks - both server-wide and specific to the database - using only the SA account.