The rows show you the notification message and the columns outline which method this will be sent.
You have three routes in which notifications can be sent; Online (within Coupa Supplier Portal), Email or SMS (text). They can be enabled or disabled partially or entirely for each.
To turn new order notifications off you will need to scroll to the Orders section and untick for the New PO Received option.
Scroll to the Invoices section and untick (as appropriate) to disable notifications for invoices.