Transactions are the things that you do on a day-to-day basis like making journal entries, writing checks, or creating invoices and credit memos.
The Entries tab on the transaction application will display the general ledger impact of the transaction by listing all debit and credit entries generated for the transaction.
Use the Notes tab allows you to record additional information about the transaction, for internal communication purposes only.
The Preview tab is applicable for any transaction that generates a business document that can be sent to the customer. Preview allows you to review the document online to verify its accuracy before sending it to the appropriate party.
Use the Tasks tab to enter activities related to the transactions. For example, you may wish to call a customer about payment or the customer may have requested a statement or copy of an invoice. Tasks allow you to record and prioritize business activities.