The name of the Odoo database you're connecting to.
When connecting to Odoo online, this value is usually the name of your custom Odoo domain. For example, if you connect to https://contoso.odoo.com, then the Database should be set to contoso.
When connecting to an on-premise instance of Odoo, you can find this value by logging out of Odoo and opening the Manage Databases page from the login screen. There, you can determine the database you need to connect to.