What are adjustments in Oracle Financials?

Are they: Credit Note, Debit Note, Prepayment, Accrual, modifying an invoice details such as the invoice amount, distribution account and GL Date, invoice correction in general?
What else would be part of adjustments (adjustments entries) in Oracle Financials?
Thank you.

You are confusing the term adjustment entries with invoice adjustments.

Adjusting Entries are journal entries that are entered at the end of accounting period.
The purpose is to adjust expenses and revenues to the accounting period where they actually belong.
They are adjustments based on reality, not on a source document.

Example:

Lets say you pay weekly salaries.
The accounting period ends mid-week.
You have accrued salary expenses that you have not yet paid.
You will need an adjusting entry to reflect the as-yet unpaid salaries so the Income Statement would reflect correct expenses.

Debit: Salary Expense 600
Credit: Salaries Payable 600

I hope that helps.

Thank you, Hasan.
I understand adjustment entries at the period end, which you have very well covered in your GL tutorials.
Now, what are invoice adjustments? Could we consider the following as part of invoice adjustments in Oracle Payables:
Credit Note, Debit Note, Prepayment, Accrual, modifying an invoice details such as the invoice amount, invoice distribution account and GL Date, or an invoice correction in general?

I would mark modifying invoice details, credit/debit memos as invoice adjustments. Prepayment is not really an adjustment in my opinion. It is simply a payment that is made before the invoice was entered. Prepayment and Postpayments would fall into payment category. Accrual Adjustements more fall into "adjustment entries" category, that is made to GL at the end of the period.

In Oracle world, I see a Prepayment as an invoice has has been paid before the final invoice arrives. And because, the Prepayment invoice has already been paid, its application does modify the final invoice the company would receive. Therefore, I am thinking that a Prepayment is having an adjustment effect on a final invoice.
I have in the past been bombarded twice with a question: "What is an adjustment in Oracle Payables"?

Adjustments are corrections to accounts in GL eg,when invoices are paid,both payment and other unpaid information are transfered to GL in a period if the period is now closed and you later find out that your payment made was wrong etc you have to do a Journal adjustment.
the key thing is ''if the period is closed.''