What is - Clickbank ID (Nickname)
Your Clickbank ID is the "Clickbank nickname" that you created at clickbank. If you have not started an account at Clickbank yet you can do that for free from here.
Your Clickbank "nickname" or "ID" is what will track your sales for you. If you do not enter the correct ID into the affiliate link you will not get commission for your sales. So it's very important you have this correct.