Yes, both have different functions, RKN.

You can see Manage Transactions in the Transactions tab. It lets you manage or record the vendor's transactions. Although, when you go to the Notes tab, there you can see the Manage Notes button. It's where you can create notes for the vendor.

I'll also include this reference about Accounts Payable workflows in QuickBooks Desktop. This will help you track the money you owe your vendors. 

If there's something else that I can do for you, please feel free to let me know.