Just to clarify, you only need to provide the client with your Account Name, Sort Code and Account Number.
They will then fill in the reference with something like 'Money I sent to Dinarius', this text will appear on their bank statement.
They will fill in Description with the text that they want to appear on your bank statement. So they might enter the number of an invoice you sent them or their customer number or their name, just something to identify themselves to you.
It is a good idea to tell the client what you would like them to put in the Description. Suppose twenty people all owe you 100 Euro each, all you would see on your bank statement would be lots of payments of 100, you would have no idea who they are from.